the screen comes with a flex that runs UNDERNEITH the grounding panel, between it, and the LCD. that extension flex often comes with either a flaw in it, or acquires physical damage via many different possible sources; handling, shipping, ESD, etc. This flex, the majority of the time, may cause the home button to stop functioning. the problem is likely this flex, if you have fully inspected the home button for any possible damage to the flex.
THIS BEING SAID, there is also other possibilities.
there may be ESD to the home button from the repair, if the proper precautions were not met. (antistatic environment)
There may be damage to the home button connector or board circuit from mishandling the device. (such as using the screwdrivers to pry off connectors, or working on the device without removing the battery.)
There may be a problem with hardware recognician. (restarting the device may fix the issue if the device was booted before being fully assembled)