Hey there clarissa148,
Thanks for reaching out to Apple Support Communities. I understand group messages are showing up as individual messages on your Apple Watch after updating. I’ll be happy to help with this.
If you haven’t already, make sure your iPhone has the latest version of iOS using the steps from the following link. Be sure to create a current backup before completing any updates as well.
Update your iPhone, iPad, or iPod touch
Once you’ve done that, see if this is happening to both Group SMS and Group iMessages. All responses in a Group SMS are sent as individual text messages and the recipients can’t see the other responses from the group. You can read more about how to identify these using this link:
Send a group message on your iPhone, iPad, or iPod touch
If the issue continues after that, unpair your watch and iPhone, restart your iPhone, and pair the two together again and see if this has any impact on the issue:
Unpair and erase your Apple Watch
Best wishes.