Not finding a satellite

I have sort of the same problem. For the last month or so I can't get a fix indoors, before that it was no problem. When I go outside it might or might not find the satellites. If I restart the watch it finds them quite quickly (outdoors not indoors).

I haven't been waiting as long outdoors as I have indoors so I don't know if it will eventually find them, but indoors I have been waiting for 20 - 30 minutes without any luck.

I'm on 18.27.

I've been noticing a lot of instability in my workouts after the update. The GPS has low accuracy.

See https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-255-series/370398/fr255s-gps-very-late-or-not-at-all

Mine normally works fine after a reboot when it gets stuck on red. Annoying but not worth it for me to try to get it replaced since I suspect it's a software issue anyway.

I grew tired of this and got the retailer to exchange the watch for a new unit, which works perfectly, with GPS lock in about 10 seconds as it should be.

I think I've posted about this before, but I sometimes get a long delay on my FR255 where the red arc stays empty. If I press BACK to leave the screen, then START to return, it usually goes to green quickly after that. You might try this workaround?