(using Google Translate)
There was an error in one of my projects.

Picture 1: When opening a file in this project, an error occurred "Failed to load the necessary language resources (one or more errors occurred). The default language resources will be used."

Picture 2: "One or more errors occurred" after opening the file.

Picture 3: Unable to use some important functions such as undo, change segment status, etc.
There is also an xml file showing the details of the error.
<SDLErrorDetails time="2021/7/8 21:48:44">
<ErrorMessage>发生一个或多个错误。</ErrorMessage>
<Exception>
<Type>System.AggregateException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<HelpLink />
<Source>mscorlib</Source>
<HResult>-2146233088</HResult>
<StackTrace><![CDATA[ 在 System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
在 System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
在 System.Threading.Tasks.Task`1.get_Result()
在 Sdl.BestMatchService.TranslationProvider.LanguageProcessingRulesProvider.GetLanguageProcessingRulesModel()
在 Sdl.BestMatchService.TranslationProvider.LanguageProcessingRulesProvider.GetLanguageProcessingRules()
在 Sdl.BestMatchService.TranslationProvider.LanguageProcessingRulesProvider.get_LanguageResourceBundles()
在 Sdl.BestMatchService.TranslationProvider.LanguageCloudTranslationProvider.get_LanguageResourceBundles()
在 Sdl.LanguagePlatform.TranslationMemoryApi.ResourcePicker.PickBundles(Object provider)
在 Sdl.ProjectApi.Helpers.LanguageObjectsCache.GetLanguageResources(ILanguageDirection languageDirection)
在 Sdl.ProjectApi.Helpers.LanguageObjectsCache.<>c__DisplayClass4_0.<GetLanguageResources>b__0(String _)
在 System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
在 Sdl.ProjectApi.Helpers.LanguageObjectsCache.GetLanguageResources(IProject project, Language language)
在 Sdl.TranslationStudio.Editor.TranslationEditor.Intellisense.TokenizationContextBuilder.Build(CultureInfo culture)
在 Sdl.TranslationStudio.Editor.TranslationEditor.Intellisense.TagFormattingDataProvider.ProcessDocumentTokens(SideBySideEditor editor, IList`1 suggestionData)
在 Sdl.TranslationStudio.Editor.TranslationEditor.Intellisense.TagFormattingDataProvider.GetSuggestionData(EditingContext context)
在 Sdl.TranslationStudio.Editor.TranslationEditor.Actions.LaunchTagFormattingWindowAction.GetSuggestionData(SideBySideEditor editor)
在 Sdl.TranslationStudio.Editor.TranslationEditor.Actions.LaunchTagFormattingWindowAction.IsActionEnabled()
在 Sdl.TranslationStudio.Api.Implementation.Editor.AbstractActiveDocumentAction.UpdateAction()
在 Sdl.TranslationStudio.Api.Implementation.Editor.AbstractActiveDocumentEditingViewAction.OnActiveDocumentChanged()
在 Sdl.TranslationStudio.Editor.TranslationEditor.Actions.LaunchTagFormattingWindowAction.OnActiveDocumentChanged()
在 Sdl.TranslationStudio.Api.Implementation.Editor.AbstractActiveDocumentAction.EditorService_ActiveDocumentChanged(IDocument document)
在 Sdl.TranslationStudio.Api.Editor.DocumentEventHandler.Invoke(IDocument document)
在 Sdl.TranslationStudio.Editor.EditorService.set_ActiveDocument(IDocument value)
在 Sdl.TranslationStudio.Editor.EditorView.OnActiveViewPartChanged(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.AbstractViewWithParts.Control_ActiveViewPartChanged(IViewWithParts view, IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl.OnActiveViewPartChanged(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl.InternalActivateViewPart(IViewPartReference viewPartToActivate)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl._tabControl_SelectedTabChanged(Object sender, SelectedTabChangedEventArgs e)
在 Infragistics.Win.UltraWinTabControl.UltraTabControlBase.OnSelectedTabChanged(SelectedTabChangedEventArgs e)
在 Infragistics.Win.UltraWinTabControl.UltraTabControlBase.RaiseEvent(UltraTabControlEventId id, EventArgs e)
在 Infragistics.Win.UltraWinTabControl.UltraTabControlBase.OnManagerSelectedTabItemChanged(Object sender, SelectedTabItemChangedEventArgs e)
在 Infragistics.Win.UltraWinTabs.TabManager.set_SelectedTabItem(ITabItem value)
在 Infragistics.Win.UltraWinTabControl.UltraTabControlBase.SetSelectedTab(UltraTab tab)
在 Infragistics.Win.UltraWinTabControl.UltraTabControlBase.set_SelectedTab(UltraTab value)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl.AddViewPartTab(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl.AddViewPart(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.WinForms.DockingViewContentControl.NotifyViewPartAdded(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.AbstractViewWithParts.AddViewPart(IViewPartReference viewPartReference)
在 Sdl.Desktop.Platform.AbstractDockingView.AddViewPart(IViewPartReference viewPartReference)
在 Sdl.TranslationStudio.Editor.EditorView.AddDocumentViewPart(IViewPartReference documentViewPartReference)
在 Sdl.TranslationStudio.Editor.Shared.InternalEditorContext.AddDocumentViewPart(IDocumentViewPart documentViewPart)
在 Sdl.TranslationStudio.Api.Editor.AbstractInternalDocument.AfterLoad(IJob job)]]></StackTrace>
<InnerException>
<Type>Sdl.ApiClientSdk.Core.Exceptions.ApiErrorException, Sdl.ApiClientSdk.Core, Version=1.1.15.0, Culture=neutral, PublicKeyToken=c28cdb26c445c888</Type>
<TraceId>b4c355be-26a7-448f-812b-640e8ed0e1ca</TraceId>
<RequestMessage />
<ResponseMessage>StatusCode: 500, ReasonPhrase: '', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
Transfer-Encoding: chunked
Connection: keep-alive
Vary: Origin
Vary: Access-Control-Request-Method
Vary: Access-Control-Request-Headers
x-application-context:
Date: Thu, 08 Jul 2021 13:48:37 GMT
Content-Type: application/json
}{"errorCode":"INTERNAL_ERROR","source":"Sdl.StudioBackendForFrontend.RestService","stacktrace":" at Sdl.StudioBackendForFrontend.RestService.Converters.LanguageResourcesDomainConverter.GetLanguageProcessingRulesFrom(LanguageResourceTemplate template) in D:\\a\\1\\s\\Sdl.StudioBackendForFrontend.RestService\\Converters\\LanguageResourcesDomainConverter.cs:line 29\n at Sdl.StudioBackendForFrontend.RestService.Controllers.LanguageResourcesController.GetLanguageResourceTemplateAsync(String templateId) in D:\\a\\1\\s\\Sdl.StudioBackendForFrontend.RestService\\Controllers\\LanguageResourcesController.cs:line 28\n at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Logged|12_1(ControllerActionInvoker invoker)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)\n at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)\n at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)\n at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)\n at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.<Invoke>g__Awaited|6_0(ExceptionHandlerMiddleware middleware, HttpContext context, Task task)","message":"Object reference not set to an instance of an object."}</ResponseMessage>
<HelpLink />
<Source>Sdl.ApiClientSdk.Core</Source>
<HResult>-2146233088</HResult>
<StackTrace><![CDATA[ 在 Sdl.ApiClientSdk.Core.RestClient.<SendRequestAsync>d__25.MoveNext()
--- 引发异常的上一位置中堆栈跟踪的末尾 ---
在 System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
在 System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
在 Sdl.ApiClientSdk.StudioBFF.StudioBFFService.<GetLanguageProcessingRulesAsync>d__32.MoveNext()]]></StackTrace>
</InnerException>
</Exception>
<Environment>
<ProductName>SDL Trados Studio</ProductName>
<ProductVersion>Studio16</ProductVersion>
<EntryAssemblyFileVersion>16.1.8.4404</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 10 家庭中文版</OperatingSystem>
<ServicePack>NULL</ServicePack>
<OperatingSystemLanguage>2052</OperatingSystemLanguage>
<CodePage>936</CodePage>
<LoggedOnUser>LIUHY\liuhy</LoggedOnUser>
<DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
<ComputerName>LIUHY</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>16533188 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>
Please help me to solve this problem.
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