I just upgraded to 10.15.4 and now the Messages app won’t load on my 2012 Mac mini, just a bouncing icon. FaceTime tells me there is an interna error and I need to Quit the app.
I use Messages on my computer all the time, not too worried about FaceTime at the moment.
Any thoughts?
Did you restart? Did you run Disk Utility?
Both are working on my laptop. Would also suggest a reboot if you haven’t already.
If reboot doesn’t do it, sign out and back into iCloud.
I ran Disk Utility, it found no issues. Also rebooted and tried to sign out of iCloud, but it doesn’t seem to do it after I choose Sign Out in System Preferences.
I click Sign out and it jumps to the iCloud icon in Sys Prefs and then doesn’t log me out.
Your Mini is just on the edge of Catalina compatibility. Did you successfully operator the machine with 10.15.3 or earlier?
Yeah, it worked great on 10.15.3, I shouldn’t have updated, I guess…
Reversion is possible under some circumstances. Not sure if you can revert to 10.15.3 
MIght be worth a try. Either that or stop using Messages/FaceTime on my Mac 
After relocating my install drive of Catalina, I installed that and I’m back to the way things were, except I’m running 10.15 and will need security patches, but not installing 10.15.4 again. I may wait and see if I can install 10.15.5 when it appears. I will also have a better backup before I do.
Thanks for the help, @anon41602260!