Cisco – Does the Cisco SPA range of phones work with CallManager/CME

Could it be asterisk is expecting caller-id but not receiving it? Just a guess as most caller-id on PSTN lines should happen somewhere around the first ring.

Have you checked with your SIP Provider has anything changed on their end?

Ours once stopped supporting a codec without notification before. If you have not made a configuration change, you should check where a change may have occurred. A lot of problems originate with the sip trunk provider, so it is a good place to check.