Text messages don't show up on my Apple Watch anymore

Can you still see the messages under Messaging? Under Notifications, try switching Messages > Mirror my iPhone OFF and then back ON again.

Good question! Try unpair and re-pair to fix it. That will restore factory settings. Start from here:

Unpair and erase your Apple Watch – Apple Support

OK. Now that fresh new iOS+watchOS updates are out, consider loading them on. Who knows they might fix this issue along the way too. Worth trying anyways.

Update your Apple Watch - Apple Support

Nope, you will basically keep all your apps and data. There are only very few exceptions to that. Check those details in here, like credit card details need to be set up again for Apple Pay, for additional security :

Back up your Apple Watch - Apple Support

Messages should come thru as well, if they are synced with iCloud.

my apple watch is not showing text messages anymore unless I go to the app

My watch is not getting text messages sent from my i phone anymore. What happened

Most welcome - glad to hear it helped :)