Check battery voltage is ok
Check all fuses
Check emergency switch is ok
Check display visually is ok, trying to turn on, but display is not getting on
Check emergency switch input voltage 24v is ok, output 24v not getting
If emergency switch coil by giving separate 24v ,output 24v supply is coming,relay no supply, display wiring no supply
Check relay & it's wiring ok,for relay no supply coming
For display wiring no supply coming
If any one have service manual or wiring diagram