first, find a firmware between 8.3.3 and 8.5.2, and install on your phone, then go for firmware version 9.x....if this not works, install a firmware before 8.3.3 (for example: 8.2.2) then install something between 8.3.3 and 8.5.2, then go for version...

maybe this help >>go to CUCM, on SIP-Trunk, once do checked & once do unchecked of MTP option.. (Media Termination Point) & see what happens..

if you enter this code >> 3491672850*#it will wipe out all data on phone, and show nothing on screen (you think its dead, but its still alive and only his network port is working and waiting for receive firmware..)then you must power up your phone wi...