hello,
I tried to upgrade the software of UC520 to the version 8.6.1 but the phones 79xx don't accept the new firmware 9-1-1 so i tried to upgarde the firmware to another intermediate version 8-5-2 but they can't register and in the firmware version it shows 9-1-1 and not 8-5-2. how can i stop the phones from loading the firmware 9-1-1 and return to the old firmware 8-3-2 or accepting 8-5-2.
