I have an officeserv 7100 and I converted two voip extensions (213 212) to internal extensions. I added in a new 4DLM card and the other two extensions are working.

When you try to dial that ext from another one (201, 202 etc), it does not ring 213 or 212.

I checked under 2.8.0 and I see them listed as US 24B set while the others are listed as 28B SET.

The old IP phone were SMT-i6021 which show their extensions now as 3201 and 3202.

Try calling a known working extension from what you think is 212 or 213 to see what number the system thinks they are. You don't say if all the phones are 28 button phones,but if 2.8.0 is listing them as US 24B, there probably isn't anything connected to those ports. US 24 B is the default state until you connect something.

My guess is you have a numbering error.

It's also possible the extensions are set to auto answer, in which case incoming calls will go directly to hands-free without ringing.

I will check tomorrow, I totally forgot about auto answer could be turned on.

Auto answer is going to go to a hands free call though, surely you would "hear " that and have a live mic at 212 or 213.
When you call from say 201 to 212 or 213 , what does the display on the originating set say? What does an idle screen on 212 or 213 show as the extension?

But I agree , if you see US24B set, that means the system has not seen a phone on that port unless it actually is a 24 b set.
Unavailable CBT would indicate no Call button but I think you have a numbering problem as well.

I changed it from US 24B to just 28B and the ringing started to work. All the phones are 28B, not sure why it didn't pick that up. First for me, thanks for the help!

Sounds like the port(s) didn't register the phone(s) correctly.
The phone type should auto change when you plug a handset in