I had the same problem and I managed to resolve it by deleting the plugin settings. Please have a look at this article:

https://gateway.rws.com/csm?id=kb_article_view&sysparm_article=KB0039988

Reply to Jutta:

I tried to follow the instructions on how to uninstall the plugin:

1. Go to Welcome view > Add-Ins tab > SDL Appstore... (which is RWS Appstore now)

but Trados crashed immediately as I clicked on the Appstore button, saying:

Set property 'System.Windows.ResourceDictionary.Source' threw an exception.

What else can I try?

Hi, please try to delete the plugin settings (its folder) on your computer. Go to C:\Users\%username%\AppData\Roaming\SDL\SDL Trados Studio\16\Plugins\Unpacked

I am sorry... I cannot find this thread. I get up to Application Data, but no Roaming (and the rest) anywhere... :-(

OK, I see the problem. You have to make hidden files and folders visible. Then you will find the folder AppData (not Application Data) and all the rest. 

To do this, open the file explorer. Select view - options - change folder and search options. Select view tab, scroll a litte bit down, and then select show hidden files, folders and drives and confirm.

OK FOUND! :-)
And when I am in the Plugins folder, do I just have to eliminate the plugin that I do not want?

I tried to do that, but the folder won't be eliminated as (they say) "the folder ot a file within it is opened in another program"... but Trados is closed, everything is closed...  :-(((((

That's right.

The message is strange, I would shut down the computer and restart it again.

Great! Problem solved!

I was also thinking to resort to this good old solution that is good for all things, but I was working and did not want to interrupt... now solved!

THANK YOU VERY MUCH, Jutta!!!

:-)

Great! Problem solved!

I was also thinking to resort to this good old solution that is good for all things, but I was working and did not want to interrupt... now solved!

THANK YOU VERY MUCH, Jutta!!!

:-)