I have an OS100, with PRI, local extensions work fine, networked from the MGI on the OS100 is a OS 7200 with a OAS card. All trunks go through the OS100 PRI. I can dial out fine from the networked system, but once the call is connected, I can not pass DTMF tones to an IVR or phone tree. They call doctors offices often and need to be able to select options. Nothing has changed that I can find. I am pulling my hair out on this one.

There is a setting in mmc210 called something like net send dtmf.
Turn this on for both systems.