I haven't yet converted my Operating System to Catalina, which is what I'm guessing is on your new Mac, so I may be on the wrong track here.  But one of the things I am looking into is the need to convert my old files that were created on my 2011 Mac and my current, 2018 Mac to run on the new Catalinia .  My 2011 Mac was running MacOS 10.12.6, Sierra and was as far as I could go on that generation of Mac.  My 2018 came with MacOS 10.14.6 Mojave and my next upgrade will be to MacOS 10.15.4 Catalina, but I have been trying to verify all I need to do to make the latest upgrade.  All warnings were that there would be glitches to anticipate.  The 2011 Mac and my current 2018 Mac are running on 32 bit processors and the new Catalina will be a 64 bit processor.  I had been warned to give the software companies that I am using time to upgrade all my programs to 64 bit and as I've monitored them, they now all seem to be compliant.  What I am not certain about however is the compatibility of my old files to the 64 bit processor and that may be related to the problems you are experiencing.  There are software programs that are apparently available for upgrades and that are relatively cheap.  What I'm worried about is just what you've experienced - will my Mac, itself, be able to deal with the changes or is there something I need to do to prepare?  Apple is really the BEST for help.  But sometimes it's hard to find the right person.  Given the current state of employment it might be next to impossible to get current information until things ease up in the future (soon, we all hope).  There may still be opportunities to find help online or by phone, but I'm sure everyone is stressed right now.  That's why I'm holding off the completion of my upgrade until everyone is back.  If you have a particular Apple expert that is still working near you, you might get lucky.  But all business nearby, including Geek Squad, is unavailable right now.