We are configuring new out of box 7962's come from factory running 8.3(2) and are having registration issues with your 7962/7915s. Our production CallManager is running 126.96.36.199014-1 and the Device Defaults for 7962 are SCCP42.8-5-2SR1S
When the 7962's initially boot and go out to load the firmware, it will immeidately get an "auth fail". We are using SCCP Non-Secure Mode. In some instances, the phone will fail to load the firmware but will still register however not many of the functions will work. I've seen one instance where the phone actually came up with the right configuration yet, in Call manager it didn't even show registered. The status was "unknown".
What we did earlier this morning was pointed a test 7962 to another 7.1(2) cluster and let the phone auto-register and pull the correct load. Once the phone came back up and auto-registered to the other cluster then we just reset the phone dhcp settings to enabled so that the phones would re-register back to the first cluster. Once we did this then the phones would be able to register fine to the original cluster.
Under the phone configuration in the device information box, the "Active Load ID" will be unknown. When you see this you will either have problems with the 7962 coming up properly issues with the Sidecar if you have a sidecar.