Fuel gauge issue

[slick willie]

I'm running a stock fuel tank and installed a new sending unit.. The gauge is stuck at ¼ tank when the sending unit is installed ( the needle does not move). I removed the sending unit and grounded it to the striker plate on the door and move the float up and down …. And it works.. but when I install it will not move… I know it sounds like a ground issue but I cannot get it to work while installed regardless of where I install it. Any suggestions