First thing I would attempt is a hard reset by holding down the power button and home button for about 30 seconds or until the phone turns off and back on. Next, I would open the phone back up to check to see if you ripped the home button flex. Even the smallest tear can cause the Touch ID to not function. If you do not see any tears, then reconnect the home button flex just to make sure you didn't fully connect it all the way. If not then I would try to update the phone using iTunes through DFU mode. To go into DFU mode turn of the phone and wait about a minute. Holding the home button down, plug the cord into the phone and continue to hold the home button until you see connect to iTunes on the screen. There should be a prompt on your computer saying update or restore and select update. If that doesn't work then I would try a restore.
If none of that works, then unfortunately the home button flex was damaged during the repair and you will not be able to get the Touch ID working again.