eatinggrumble84 its still working for me. If you're using Google Messages while logged in, try doing this first:
Confirm all Sandboxed Google Framework and Google Play Services are installed on that profile. Make sure play services has access to at least Network, SMS, Notifications.
Install the actual Google app from the Play Store if not installed already. Give it access to at least Network , SMS, Notifications.
For Google Messages, give it at least Network, SMS. notifications. I also gave it access to contacts and phone, but it may not be necessary. You may need to reinstall the app if it's not letting you try to verify.
I do not have Google's carrier services app installed.
After doing everything above, close google messages (to be on the safe side). Open the Settings app on your phone. Go to:
-> Apps
-> Sandboxed Google Play
-> Google Settings
-> All Services tab (for the google account you're using with Messages)
-> Mobile data & messaging
-> Phone Number Verification
Toggle Automatically Verify Phone Number (s) to on.
Afterwards, re-open Google Messages and go to the RCS section of settings. It may already say connected or try to verify again and see if it connects this time.
Hope this helps!