New gasket on fuel sender and now my guage doesn't work!!!

I fitted a new gasket to my fuel sender unit yesterday coz i had abit of a fuel leek from it and now my guage isn't working!!!i was v.careful with the unit and don't think i damaged it atall, all the connections seem fine and i'm pretty sure i put it back in the right way-i've even had it back out to make sure the float is free to move and it seems like it is. Its a gsi if thats any help. Any suggestions? I think it might just have to be a new fuel sender unit :(