Joel Henderson 

The problem you face is probably the one described here:
Trados Studio throws the following error: "Key not found: 'e404caca-1efe-b1e5-369fd17b8b14'. Parameter name: Key" (sdl.com)

I suggest you do a RESET of Studio according to these instructions:
Reset Trados Studio to its default state (sdl.com)

Walter,

Thank you for your suggestion. I've given it a try, but the problem still persists.

Joel Henderson 

Go to View and select "Reset window layout" in all views of Studio. Restart the program. Go to File -> Setup -> Manage user profiles and reset the current user profile. Restart Studio and reset window layout once more. If this still does not help, go to user profiles management again and select change user prpfile. Do not backup the current user profile. When you come to the selection screen, chose Browse and navigate here: C:\Program Files (x86)\Trados\Trados Studio\Studio18\UserProfiles
Chose one of these profiles and in case Studio will ask to overwrite any settings confirm this. Restart Studio, reset window layout once more and restart for the last time.

After that you should be able to work with Studio properly.

Jerzy,

The first option didn't work, unfortunately. I tried your second suggestion; however, when I came to "Browse and navigate here", I wasn't able to find any user profile with the prompt you sent. Any suggestions?

Joel Henderson 

This path is for Studio 2024. Please check on your hdd c:, where Studio is installed. TS2022 may be installed in SDL instead of Trados. The path structure is however similar.

Unfortuntely, it didn't work.

Joel Henderson 

Sorry to hear that. Does this apply only to one project or is this a general problem?

This is a general problem - I can't open any files or create any projects.

Joel Henderson 

In this case, if even resetting Studio according Walters suggestion does not help, my last ressort would be the article here: https://gateway.sdl.com/apex/communityknowledge?articleName=000001414

Should this not help either, please come back and let us call Trados to this problem.

Perhaps this issue should be brought to Trados's attention. I don't have the option on my computer to repair apps, and I've tried all the other solutions.