Mini2 home button stopped clicking and working. How is click made?

This happened months after I last opened it to replace the battery. All other mechanical switches, and the digitizer itself, still work fine. There are few complaints to be found on the net about the home button 'snap', so apparently the mechanism is pretty reliable.

I reopened the mini 2 to check for shorts or missing insulator tape, that was all fine, though I re-taped the trouble spots just in case.

Looking at the home button assembly I cannot figure out how the tactile snap/click is even made. Is there a flex dome in there, or some tiny spring lever? I closed the iPad back up, and there was no change.

I believe that the digitizer assembly (front panel) iPad mini 1/2 Screen Digitizer includes the entire button assembly, (including the clicker?), but the description says, "PART ASSEMBLY INCLUDES ...Blank Home Button, Digitizer Cable...". I don't understand what is meant by "Blank Home Button". Does that include the button face, the switch assembly, and whatever provides the tactile snap?

Thanks,

Taryn