What happened to my Touch ID button?

I took apart my MacBook Pro to replace the thermal paste today and when I put it back together, everything worked fine… except for the Touch ID sensor and its button.

I can’t use Touch ID and pushing the button does absolutely nothing whether the thing is on or off. Is there a connector inside the machine that I forgot to reattach which makes the button work, or could something have been irreversibly damaged?

Nothing else seems to be amiss and I can deal with not having a power button in regular use, but if the computer stalls I want to have that failsafe.