hopefully this is just a connection issue. often times when we replace screens or other parts of the device we may not put everything in place like it should be or even worst and i really hope this is not the issue, but we bend a piece. I would try to take the device apart again and check every connection and reseat them all just to make sure i did it correctly. look at every connection to make sure it is straight and not broken. if needed use a tear down guide to compare what you have with another working model. if you have another device try the same parts from the damaged one on the known good one and see if you are having the same issues to eliminate which part of the device is the problem. reconnect everything very carefully and see if you have the same issue. i hope that this is helpful and that your ipad is up and running like new in no time.