Automatic Wipers

Probably been mentioned before and there is probably an easy fix, but my automatic wipers are not working.

I noticed that there was no gel pad between the sensor and the windscreen, so I purchased a replacement one and it hasn't fixed the issue. I have turned the wipers onto the first option, and then twisted the dial and the wipers go once and then not again. Could the sensor not be pressing hard enough onto the screen?? I was going to purchase a new sensor off eBay but don't really want to unless there is no other option.

Thanks!