i saw there some issue that if we erase user area before flashing but there is issue in no service while we erase all data. but i found solution with following trick i think help this
1. first identified devices in qualcomm tab this will show you all partition of your device like GPT main, aboot, sbl1, etc.
2. erase first partition of your devices which names as "GPT Main" by tick partition and erase tab
by this you will erase all information of your user area dont"t worry
3. again flash stock firmware with proper firehose identification. in this process you will need to write again imei after this you will solve your devices problem.
note:- this is not suggestion but this trick solve my same issue for no service with qualcomm plateform.