Hi @paul.glover, welcome to the Community!

I’m sorry to hear that you’re having trouble registering your Play:1 speakers. These are a steps I would recommend and have heard have worked for our community members:

1. Sign out of the app by going to Account → Sign Out
2. Close and re-open the Sonos app 
3. Sign in with your Sonos account details
4. Select the Play:1s and follow the in-app steps to register them.

If you’ve done the above and registration fails again, then I’ve seen users mention that transferring system ownership but putting in your current details when prompted for the new owner details can also fix this issue.

If the steps listed don’t help, then I would recommend submitting a diagnostics and reaching out to our support team for further troubleshooting.

I hope this helps!