Chosen Solution
iPhone 6s Plus, swapped out the display assembly. At first, Touch ID would not work at all. Took working ribbon cable backplate from the original cracked screen and swapped it onto new part. Now Touch ID sort of works. The Add Fingerprint option is no longer greyed out, but selecting it gives me the usual “Unable to setup Touch ID” Do I have a defective part? Perhaps a loose cable?
How did you manage to transfer the home button extension cable from a 6s screen? Probably damaged the home button extension cable on the old screen, you would need to get another screen as the home button extension cable on all the screens seem to be faulty. Try getting the replacement screen replaced under warranty from your supplier.
Hard reset should solve the issue
