Loud beep in video!

Use a multimeter to check continuity of the switch in question. When the button is pressed the terminals should be connected (multimeter should show a very small resistance and audibly beep).

I show here testing the switch after removing from PCB. This is NOT required! You can test the switch before desoldering from PCB.

Video part A: Shows how a working switch should behave.

Video part B: Shows that the broken switch does not respond to button.