No green light?
Disassemble the transmitter and tap the crystal with power on. use non conductive tool !
The crystal is up front and has a shiny case.
I suspect a component value has changed and the oscillator circuit fails to start.
By tapping the crystal it starts the oscillator.
This makes the unit work until power is removed.
…or give the unit a sharp slap with the palm of your hand…that gives same result
..anyone have a circuit diagram to post? I may be able to determine the fault.