Hi Creamyhamstrings,
Thanks for reaching out to Apple Support Communities. It sounds like you're having an issue with Activity notifications from a friend on your Apple Watch. We're happy to help.
We recommend checking to ensure all the settings outlined in the article here are correct: Share your Activity and compete with friends with your Apple Watch
You can also check how to customize and receive notifications for specific apps on your Apple Watch here: Notifications on your Apple Watch
We also recommend checking how you have your friends contact information set up on your devices. You can also pass along the information to ensure your friend has your contact information set as your cellphone number and not your email address.
Cheers!