Messages showing users offline
I saw an exchange about this in 2015, but 3 years later, I thought I'd start a fresh one, because it didn't look resolved. Messages, the texting app on my Mac, is showing everyone I'm in conversation with as a highlighted red. Anything I send is not received. My Messages app on my iPhone 5s (yes, old), is working fine with these same people. Bonjour shows a green dot and "Available," my status on the menu bar shows a green dot and "Available," but when I click the recipient's name, it shows their phone numbers grayed out.
MacBook Pro, OS X Mountain Lion (10.8.5)