It seems to me that there is an indication in these lines of the original posting:
Mar 9 10:22:49.794: Se1/0:30 PPP: Treating connection as a callout
Mar 9 10:22:49.794: Se1/0:30 PPP: Authorization NOT required
Mar 9 10:22:49.794: Se1/0:30 PPP: No remote authentication for call-out
Mar 9 10:22:49.906: ISDN Se1/0:15 EVENT: UserIdle: callid 0x80B1 received ISDN_
From that I believe that your router is going through normal processing of the call and that it received a hangup/disconnect from the remote device. I suspect that the issue is more likely on the remote device than it is on your router. If I were guessing at the problem based on the little information that we have so far, I would guess that it is an authentication issue on the remote device.
If you believe that this is not the issue then perhaps you can provide some more detail about the problem. The output of debug ppp negotiation might be helpful.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...