T1 robbed bit to 3rd Party IVR does not communicate with IPO 500 9.1

[mrossk]

Good Morning,

we're having an IVR Server running with a T1 CAS.
right now, the old PBX (Nortel Meridian) simulates 24 Analogue Channels with Loop Start.

Client calls in on ext. 100, call is being forwarded to 121-145. IVR answers on first available channel

New Situation:

The Vendor (IVR) gave us all Specs to connected the Server to the new IPO 500 9.1.:

D4, AMI ZCS, FX, Loop Start.

So far so good.

You can see the Line communicating with the IVR, but I do not get a Voice connection. It immediately says Line Down (on the IVR).
when dialing the Incoming Line ID of a channel, the channel opens and shows connected (in Sysmon)

My question:

How do I simulate Analog Extension (members of group 100) and route them the IVR behind the T1 robbed bit?

Vendor is Edify, No Document in DevConnect,

Summary:

T1 CAS to IVR
need to 24 Extensions routed to IVR
Extensions need to be member of Group 100
IVR can forward call to group 110 to talk to a Call Center Representative

Your Help is appreciated!

Thank you very much!

Cheers

Mat