I faced this problem of lost IMEI about a year ago and asked help here at smartron. Well, they couldn't help. I went to the service center and asked for help there. They didn't do anything except deleting my data by flashing the stock rom and yeah they said that they could change motherboard to which i straightway refused. I tried many things to fix this but couldn't fix it for much time. Then I found a way and i am going to share it with you.
Download this: https://androiddatahost.com/wp-content/uploads/qualcomm-smartphone-write-imei-tool-v1.01.zip
Use it. It's pretty simple.
The Qualcomm drivers should be there with you from the QPST installation. If they aren't, simply install QPST. That's the sure shot way of installing proper drivers.
1)CK Telecom, for the IMEI tool
2)Qualcomm, for the drivers
3)Smartron, for this platform
I have nothing to do with it except sharing it with you guys.