Layout refuses to open recovered file

My layout file will not open or save properly. Leading to recovered versions of work completed that it simply refuses to open no matter what. I dont want to keep starting over only to lose the work and waste more time. There’s no reason this file should be corrupt, but is there someone who can open my file and advise? I’m on the classic 2020 version and suspect Sketchuip wants to make this as inhospitable as possible to push people to subscribe to their support less subscriptions…

What version of MacOS are you using?
Are you saving to the cloud?

MacOS Monterey v 12.1 and it backs up to dropbox. I think the sku file was saved as 2021 at one point, so I’ve saved a 2020 copy of both now. Not sure if the glitch is resolved but I’m at least getting some responsiveness now. Ever since I updated once last year I have to right click and open as the old version or else it will convert to a newer version that doesn’t sync.
Also I can’t close a single sku model - it opens the last seven I’ve been working on at once, and if I close one they all close! Lots of weirdness trying to stick with 2020