had a phone plugged in as ext 11, it may have been plugged into a co line at some point and stopped working.

I replaced with an untested phone and that too is not working. however the smaller phones work fine.

is there a place to tell it to be one type of phone versus another? (4-51 dictate the line keys)

Is there a different wiring needed for it? (1st pair instead of second pair?

First pair, WH/BL-BL/WH. Key data is 4-12. There is no telephone type programming. Try a working phone at the DMARC.

So all of the other phones run off of the second pair, but this model runs off first pair?
If that is all it is I will kick myself and owe you a beer.
Now I know the reason why I never got into the IPK side.