First start by calling 1-800-comcast and ask a rep to completely remove that modem from your account and to "re-provision" it from scratch. Also ask them to confirm that the provisioning and account data in their database is correct and complete. Make sure that they are using the correct CM / HFC MAC address for the "home modem".
Hello Kare429. Welcome to the Xfinity Forums and thank you for creating your first post. I can assist with further troubleshooting your modem that keeps returning to activation. Please reach out to me via private message and include your full name so I can assist you. To send a private message: click my name (ComcastJoeTru) to view my profile. Then click the link that says "Send a message" and there you can private message me.
Hello Kare429. Thank you for private messaging me. Due to elapsed time with no private message response from you, this thread has been locked. If you still need assistance with the matter, feel free to respond via private message or create a new post and our team would be more than happy to help you again.