WARNING chan_sip.c: Timeout on [SID] on non-critical invite transaction

I’m running into the same issue with a new install. Trunks are up, but keep getting the same error about a timeout on a non-critical invite.

Does anyone have any ideas as to where to check for clues? Neither the Asterisk console nor the log file are giving me much.

PBX Firmware: 6.12.65-22
PBX Service Pack: 1.0.0.0
FreePBX 12.0.32 to be exact.

Log file says simply:

[2015-01-19 02:03:33] WARNING[1945] chan_sip.c: Timeout on (SID) on non-critical invite transaction.

Thank you all

Uri