Sameh Elsharkawy 

Thank you for the stack trace error as its so helpful.

If you take note the stack trace mentions

Sameh Elsharkawy said:

<Source>Multilingual.Excel.FileType</Source>

Is your intention to create multilingual excel project (relying on the plugin) or on out the box excel file types that are support by default, Excel or Bilingual Excel.
Check the file type being used when you create your next project.

Looking forward to your clarifications

Lyds

Not at all Lydia! I am trying to create a project for a one column Excel file! See the screenshots attached! Something is really wrong! Should I deactivate the Multilingual File type?

even deactivating the Multilingual Excel file type did not work at all! 

<SDLErrorDetails time="2/26/2023 5:56:04 PM">
<ErrorMessage>Object reference not set to an instance of an object.</ErrorMessage>
<Exception>
<Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<HelpLink />
<Source>Multilingual.Excel.FileType</Source>
<HResult>-2147467261</HResult>
<StackTrace><![CDATA[ at Multilingual.Excel.FileType.Services.BilingualParser.GetExcelColumns()
at Multilingual.Excel.FileType.Services.BilingualParser.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.Parse()
at Sdl.ProjectApi.AutomaticTasks.Conversion.ConversionTask.ProcessFile(IExecutingTaskFile executingTaskFile)
at Sdl.ProjectApi.AutomaticTasks.AbstractFileLevelAutomaticTaskImplementation.Execute()]]></StackTrace>
</Exception>
<Environment>
<ProductName>Trados Studio</ProductName>
<ProductVersion>Studio17</ProductVersion>
<EntryAssemblyFileVersion>17.0.5.14757</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 10 Pro</OperatingSystem>
<ServicePack>NULL</ServicePack>
<OperatingSystemLanguage>1033</OperatingSystemLanguage>
<CodePage>1256</CodePage>
<LoggedOnUser>ADMINSAM\Ahmed</LoggedOnUser>
<DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
<ComputerName>ADMINSAM</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>50276084 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>

Two thoughts.

1. Can you successfully create an XLIFF file from another, new Excel file? If so, then there must be something non-standard about the Excel file you want to translate.

2. Not-very-satisfactory workaround: if all else fails, you could copy/paste the Excel cells to a Word table, translate that, and then re-create the Excel file. But like I say ... not very satisfactory. And of course unworkable if you have Excel files of any complexity, with formulas.

Sameh Elsharkawy - just check as there is a difference between File - Options (default settings) vs create project and from within the create project wizard you then assess file type settings.

As Steve Rawcliffe suggested, does this happen with other excel files?
What happens if you dont create a project through the project wizard, but Translate Single Document?

Looking forward to your clarifications

Lyds

Please see the above. I think it is an issue with that Multilingual Excel file type!!!