My prints are failing and I can't figure out why

I’ve had my Tronxy for over a year now. I’ve learned a lot thru trial and error and have gotten some really good prints. I use Repetier slicer. A couple of days ago I started having problems with prints falling apart. I have tried changing filament, changing setting, changing temperature, changing models. I triple checked the bed level. When none of that worked I changed the nozzle thinking for sure that it was clogged. Still no luck. I can print flat on the bed OK, but anything with any kind of wall or feature that builds up off the bed doesn’t stick together. My last test was to try a desk top organizer that I printed successfully just a couple of weeks ago with the exact same settings and temp and this time it failed… I don’t know what is wrong. Anyone have any ideas about what is causing my problems? Thanks.