Time Machine backups not recognized after SSD replacement

I am no expert in this but this is what I did:

Using Finder, opened the last backup file before the SSD and OS upgrade was done and navigated to folders such as Documents, Downloads, Music and Pictures and copied all the file back to my new OS.

Followed the advice in this link to reinstall apps I had acquired from the App store:

How to install Pages on macOS Catalina ve… - Apple Community

Followed the advice in this link to reinstall Microsoft apps such as Word, Powerpoint and Excel (I had an Office 365 subscription):

https://answers.microsoft.com/en-us/msoffice/forum/all/office-365-on-mac-os-catalina/82b8e0c3-d364-4bb3-82e3-5c291ff0ac42

That restored my iMac to a very large extent but with Catalina. A few third-party apps were beyond redemption as they will not work on Catalina.

Did your engineer create another user’s account, perhaps to check out the repair/upgrade? If so, you might find that backup opens with this. I found that, as a usual user, some of the file permissions in the backup folders denied me access but the second user created by the engineer was allowed.

Good luck!

I am in a similar predicament. My fusion drive on High Sierra was replaced by an SSD and the OS upgraded to Catalina. I was unable to get TM to read the High Sierra backup files but managed to recover documents by opening a backup in Finder and copying them back to the Mac. If you find a solution, please post back in this thread.