Sounds like an incomplete circuit or being out of range.
(Happens with my DVD remote)

Detector out of range of the signal "cone" ?
Failing detector?
Corrosion left behind from prior battery?
Membrane switch of the button starting to fail?

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022