I woke up this morning to find a message on my iPhone that did not show up on my MBP. I have no idea why, seems completely random. Had the same problem in Catalina.iMessage on Big Sur does not properly sync with my iPhone 12 Pro Max
No matter how many times I sync, there are messages missing
I did an entire reset by logging out of both my Mac and iPhone, changed my iCloud password, restarted everything, logged back in - still missing messages
Plus, the 2-steps required to delete messages and the Archive function being useless
Who would have ever thought we'd long for the days of Catalina?
I thought that it had been fixed but I guess not. š„