You may have gotten a bad part.
However, I would ask you why you changed your screen first? Was it because it didn't respond to Touch? The iPhone 6Plus is well known for suffering from Touch Disease. You can click on my profile for a link to an article on this problem or search the web.
If you were just changing a cracked screen and the touch always worked fine before, then you may have incorrectly seated the digitizer connector on the logic board.
Go back through this guide to make sure everything is okay. The connectors are very delicate but should still "snap" into place. Also be very careful to track your screws properly and always disconnect the battery first.
If the replacement screen still does not have touch, then ideally you would need to put the old screen back and see if it does the same thing. If you can isolate the problem to the new screen, send it back for a refund and only buy from reputable companies.