I got this response when I contacted my watch developer (Mobvoi) with this issues

"Our engineering team have contacted the Google team about the compatibility of this app. They told us they will contact Verizon. The problem is with the app. They will fix this problem in next version. I am deeply sorry for the inconvenience.
If you have any further questions or concerns, please do not hesitate to contact us again.
Best regards,
The Mobvoi support team"

II have emailed the verizonmessages app email a few times, and have just gotten a generic response both times so far I have sent an email.

Doesn't really solve anything, but some more information at least.