Hello Kevin,
To rule out an issue with the PA system can you connect an analog phone to the SPA8800 and make some test calls to that phone?
If the analog phone can't make/receive calls, I'd like for you to do the following:
1. Post a copy of the UC's running configuration here(removing username/passwords, public IPs, VPN preshared keys, etc).
2. While running the following debugs, please reproduce the issue and post the debug output here.
2a. debug voice ccapi inout
3a. debug ccsip messages
Finally, what is the PA device being used?
Thanks,
-john