Liquid transfer pump stopped working

Sailnovo Battery Operated Liquid Transfer Pump

I have this liquid transfer pump above. It is not the highest quality device but it is extremely useful to transfer gas without spilling. It uses 2 D batteries to power it. I think I dropped it and now it it does not work with the On/Off switch.

When i futz with the lid which has the power switch and push I can sometimes get the pump to come on so I think the pump is working fine.

I have attached 2 pictures of the lid with the switch. If I could get some hints to understand what the switch is doing and how i might make something that does the same that would be great. i could also just force it to be on when i screw it in and just unscrew the lid to turn off. that would be fine.

thx