You've upgraded from Trados Studio 2019 to Trados Studio 2021. But now, unfortunately, the Trados 2021 version is not functioning properly and it throws error messages such as:

Could not find a part of the path
Failed to save bilingual as: Could not find a part of the path
Failed to add file to the project
Could not find file 

1. Search for 'Storage settings' in Windows and check if the Storage Sense is On; if it's not, please activate it:



2. Check if there are inactive TMs in your projects and, if there are, remove them. You would find them in Trados Studio > Project Settings > Language Pairs > All Language Pairs > Translation Memory and Automated Translation: