Default [Q] Yuntab p500 try to load rom


I have a yuntab p500 and am trying to reload the original rom as it is stuck on only looking for / using 2g services

I have rooted phone and have downloaded a rom and QPST program . when i run it it fails on putting phone into download mode

i have tried to load a OTA and bin file form the sd card but keep getting the e verification error

Are there any yuntab users who may be able to guide me to fix the problem to run on 3 n/w in the UK

Thanks in advance,