Hi Jast123,
Thanks for reaching out through Apple Support Communities for help with this alert message you're seeing when attempting to share your name and photo in iMessages. We're glad to help!
In order to use iMessage name and photo sharing, you'll want to ensure that the same Apple ID is signed into iCloud services and iMessages.
To check, first head into Settings > [your name]. Verify that your Apple ID is showing here.
Next, head into Settings > Messages > Send & Receive, and check that your Apple ID here as well.
We've got a great resource to share with you that has recommended steps to get name and photo sharing set up. Let us know if this helps, or if you've got any questions:
iMessage name and photo sharing
Have a great day!