I have Verizon Message+ app (9.3.0) on my Android (Google Pixel 6 Pro - v.13) . I also use the web-base Message+ app on both my iMac and MacBookPro. (both OS = Mac BigSur 11.7.6)
Normally the devices all show on my settings page under "Manage Devices". However none of them are showing any devices linked. (see attached screenshot)
This is a recent development; I don't know when it stopped.
However messages haven't been syncing between the devices accurately for several weeks. Please advise?