I get the following message randomly throughout the day on a phone that is logged in remotely to the PBX: The IP 107.xx.xx.xxx has been blacklisted for 3600 sec. Reason: Too many failed authentications! I am using a Yealink SIP-TP22P with the latest firmware. I have a remote office, so the phone connects to the 3CX through my TP-LINK router, then the Time Warner Cable modem then into my router at the main office. The password is obviously correct because it logs in and works just fine for most of the day. However, 2 or 3 times a day the phone will stop working and I can see it is blacklisted. I have to unblock it and it works again for a while. What could cause this problem? Is there some kind of debugging to figure out why it is being blacklisted? Either on my network or on the PBX, etc? Could it be caused by my TP-Link router somehow? Bug in the phone? Once it registers, why does it it fail again? Is something set to force re-registration on a regular basis?