Why a non-responsive digitizer but the LCD video is fine?

I dropped my phone and cracked the screen and the digitizer stopped working. I purchased a replacement LCD and digitizer. I installed the new component and the video was perfect however the digitizer was still unresponsive. I reopened the phone and re-connected all the connectors, but still no response from the digitizer. Is there a way to know that the digitizer I purchased is not faulty? Is there a second component that I should replace that could also have been damaged as a result of breaking the screen? Do I need to totally reset the phone in order for the processor to recognize the change? I only powered it down.

Any other suggestions wold be greatly appreciated.

I have successfully repaired 3 other phones, I'm not a total newbie.