Home button touch ID issue

i disassembled a 6s to install a new battery and replace the back camera. it's been sitting in two pieces for a month or so. when i went to reassemble, everything worked except touch ID.

Touch ID worked before. no screen components were changed. the home button works fine and 3utools reports that the home button serial number that the phone expects and the serial number of the button match.

there is no warning that the Touch ID doesn't work because it is the original button, just nothing happens when i put my finger on the button.

i've checked the home button connector (even though i didn't do anything with it before.

i've reset settings.

i've erased the phone.

i've upgraded to latest IOS.

are there any troubleshooting steps that i haven't thought of or things to try that i haven't?