Key / remote not working checked the obvious. It is the one button separate remote. Any one able to help me out?

 

Hi mate. I had the same problem years ago is it the blue fob with one button?
The problem I found was the solder was cracked on the arm that sits on the top of the battery. Just put clean the old solder away and put new on. But fiddly to do as the arm moves when you desolate it but should sort it out.
Kev