I had this issue last week. In my case, it turned out that the caller ID information was not being passed as a facilities IE Message. By unchecking the "Get Incoming Caller ID Name from Facilities IE Message" in the Telephony -> Ports and
Trunks -> PSTN Trunks -> T1/E1 Tab, the caller ID information was properly displayed.
If this does not correct your issue, check with the PRI provider to ensure that Caller ID is being passed by them, and what method they are using.