I am unable to send text messages to *certain* people after upgrade to 24-inch iMac
iMac 24-inch M1 2021
Big Sur v 11.5.2
Sending messages to some people that I could before the upgrade to 24-inch doesn't work. Most yes, some no. Even replying to previous threads doesn't work. I note that these folks are generally "green" while the most successful are "blue." I can't find any setting that even comes close to addressing the problem.
Note on the attached screenshot that I was able to send previously, but now fails. The last message followed upgrading to the latest version 11.5.2.
iMac 24″, macOS 11.5