Apps not working on apple watch after
After last firmware update some apps stop working
First force restart it
i.e. press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo.
If that is no help
Unpair and erase your Apple Watch
and then
If no better you may want to unpair then set up without restoring the backup.
If still no good ensure you have no security apps on the iphone that may be mirrored on the Watch, or any out of date apps that have an available update in App Store