Retracting step switch

[Figaro]

On starting the van yesterday the buzzer was sounding for the step even though it was retracted.
Looking at it, it appears the switch is mounted in the plastic cover that has cracked so switch no longer lines up when retracted.
I'm hoping a bit of fibreglass will repair and strengthen it but I'm having trouble getting the cover off.
Only one screw visible in centre of cover and is not moving once screw removed, don't want to force it and break it, anyone know how the cover is held on ?
Not sure of make but its a 2003 Hymer double step.
TIA

 

[Figaro]

All fixed now with a bit of fibreglass repair, there are two screws in the cover, the second one was obscured whilst lying down underneath, but can be just seen in photo 2

 

[Canyon904]

I found a lorry wheel flap on the road and fitted it front of the step to keep the road crud off and minimise any damage to these micro switches, three yrs on and still no problems.