Do you guys have any logging facility? It would be relatively easy to troubleshoot these issues if rf2 traced the MM dialog results into a simple text log file. Then we could just upload the log file.
Anyway, I got the greyed out join button too, 573 client against 573 servers.
I joined one of the ISR servers (Meganes at Monza League or something like that). Stayed there for half an hour.
After I left the track and returned to the MP lobby, all the 573 servers had join button greyed out, which made me think it could be (my) client issue.
BTW, the "greyed out join" manifested itself exactly as it does in 494. The details about the server in the box to the left were not complete.
I closed the MP lobby. Restarted from launcher + MP and everything was back to working state again, so it looked like it definitely was *not* a server issue this time.