If layer 2 is deactivated meaning if it does not say MULTIPLE FRAME ESTABLISHED when doing a show isdn status command, then that could mean your ISP changed their setting on their ISDN switch. You can try to do a debug isdn q921 and shut, no shut the BRI interface and see what the output displays in the debug.
If bouncing the interface does not fix the issue..its time to pick up the phone and give your ISDN provider a call.
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...