Yealink T28p no longer working after CudaTel firmware update

[AshElsayid]

I have about 35 Yealink T28p phones that were all working fine using the 2.60.0.153 firmware. I, over the weekend, upgraded our CudaTel VoIP firmware to version 3.0.004.016. After this update was completed, the Yealink phones updated themselves to firmware version 2.72.0.26. This morning i have found that none of the phone are working at all. All phones show "obtaining IP address". I have tried factory reset to the phone, and still no provisioning is happening. One one extension, I entered all the network setting manually, and after a restart and provision, the user get his extension to show on the phone, but when calling the extension, it goes right to voicemail.

Any help would be greatful as Yealink is based in China and has no US offices.