Screen replacement iPad pro

First, was your iPad turned off when you did the repair? If it wasnt, something could have been shorted with connecting and disconnecting the flex cables.

Second, I would inspect the connections on the logic board to make sure none of the pins are bent as well as inspect the flex cables.

Lastly, there’s a good chance you broke the digitizer of the old screen while taking it apart and the new screen is defective, so as a triple check I would try another replacement screen just to make sure.

If none of that works, its most likely going to require a micro soldering repair.