Messages and FaceTime won't activate on MacOS

I'm using Messages fine on iOS, but on my MacBook I signed out but can't get back in.

I'm running 10.15.3 Catalina. I've rebooted, have a strong WiFi connection, my date/time is accurate. I've seen online references to opening Messages Preferences and checking/unchecking "Enable this account" but that must have been on an older version of Messages because it's not visible to me.

I was having this Messages issue while FaceTime was logged in and working. I signed out of FaceTime, and now I'm unable to log back in (no error, just re-displays the Apple ID/Password fields again.

If I go to appleid.apple.com, I'm able to log in with the same Apple ID and Password I tried with Messages and FaceTime. Now I was prompted for a 2nd factor, which I wasn't for Messages and FaceTime, if that's relevant.

I also tried resetting NVRAM to no avail.

Any help appreciated!