After recent update for Apple Watch 8, I can receive text messages but am unable to send

Hello VictoriaBrooklyn,

This page can help out with providing some steps that may be able to resolve that issue with sending texts: If you can’t send or receive messages on your Apple Watch - Apple Support

If you see a red exclamation point  or "not delivered" next to a message, tap the alert to try sending the message again. If the message still won't send, try the steps below. 

The page will help to go over more info on each step, but will cover the following:

1. Check Control Center

2. Check your connection

3. Try sending a message from your iPhone

4. Make sure that you signed in

5. Check your iMessage settings

6. Sign out of iMessage

7. Sign in to iMessage again

8. Restart your Apple Watch and iPhone

9. Check for updates

As the page notes, if the steps haven't helped the next step would be to unpair/erase the Apple Watch and then pair them back together before reaching out to Apple Support: Unpair and erase your Apple Watch - Apple Support

Cheers.

Same for my Apple Watch Ultra as well as my partner’s Apple Watch Series 8.

they receive messages but they fail to send messages. Especially, it seems, when replying to Fitness Activity alerts.

We’ve reset the watches to no avail. I am not going through the entire restore process with both watches. That’s utter nonsense, and will very likely not resolve the issue.

I’m hoping the WatchOS developer team finds what caused the issue and issues an update. We just, sadly, won’t congratulate friends and family for their accomplishments until then.