I have a Conference Max phone that refuses to ring. Checked levels and checked programming to the port, it's identical to the other fax/modem lines. The phone dials out fine.
I'm missing something stupid.

have you checked the phone with another working analog phone? or Take the conference max to the fax machine line and connect it there and test.

sorry yes, I tried a dumb phone and it dials out as well but does not ring.

How many analog devices are connected to that extension? You may have exceeded the Ringer Equivalence Number.

Also, check other analog devices on that same card. Do they ring?

Have you reset the system since the problem began?

Try use access code on PRG 11.11.16,Enable Force Ringing of Incoming Intercom Calls.

Only 3 devices including conference phones.
The same dumb phone I used to test the above with rings on other analog ports and Fax machines ring.

Straight from the files of dumb, here's what happened.

I kinda had to reconstruct events from the last time I actually heard the phone ring. It was a while back (8 mos). Since then we have installed the SV8100 (formerly IPKII). I had scheduled the cut over at 10:00 on a Wednesday (only day the tech could make it). That was also the day of our weekly meeting with our offices in various states. Since we use webex for conference services and everyone knew of the cut over I assumed everyone would call on their own accord. however to my astonishment everyone at our brach was sitting in the conference room wondering why the phone wouldn't dial...
OK, so with the other half of the company waiting on hold in the Webex lobby, I frantically run to the tech and ask if he could do a quick punch for DID 670 to an analog line. The switch was in and the programming done, so he promptly punched. 2 minutes. The conference line was up. I apologized to him, dialed the webex number for the meeting participants, done. Went back to assist the tech and keep the offices busy while the remaining lines were done. 15 minutes tops.

I joined the meeting after about 30 minutes after the tech had left. Never thought about it again.

Since the conference phone dialed out, I never bothered checking the station port on the block. So I went today and was looking through the DID translation table to what I knew were the analog ports on the block...yep...that emergency punch went to a different station port than in the original programming (on the old IPKII [the switch was programmed offsite]). The emergency punch.

Long story short, 22-11 was pointing to the wrong extension in relation to the port (11-02). Changing the DID translation obviously solved the problem.