Backup problem has reset my catalogs

I am on a Mac running Catalina 10.15.6.  I moved a catalog to an external drive improperly. I was able to reset the catalog location to the external drive. I then had to reconnect all the files, about 100,000 of them.  It took me almost a week of manual and automatic reconnection.  I then did a backup of the file structure only.  At the end of the process I got a message that the catalog couldn't be found and to create a new one or open another. I opened another (I have 3), and then went through Manage Catalogs back to the catalog I had been working on.  All my reconnections are lost. In addition, none of the files that I have imported since mid-November are showing.  This is also true of my other catalogs as well, all of the files since mid-November are not in the catalog.

What happened and can I fix it?