htc desire 626 display have model? cant be used aftermarket display

@roshanprab37388 that could be caused by a failure within the matrix of the LCD screen. Sounds like it is not receiving any video signal. There is not a lot you can do about it other than checking the connector to make sure that there are no bend pins or corroded contacts. After that, you will have to replace the LCD display.

Since iFixit does not yet have a guide for this, use something like this video to work on it. Replacement screens are still available at places like this and a few others. It is getting more difficult to find them for HTC phones.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.