3cx Firmware blocking firmware upgrade

[M1n3rva]

Recently I've used one of the 3cx firmwares to upgrade my Yealink T46S up to version 66.86.0.15 (https://www.3cx.com/docs/phone-firmwares/) and it blocked any firmware change on the device.

Any help would be greatly!

 

[TheodorosG_3CX]

What exactly mean that is blocking?
Are you trying to downgrade?