First, make sure it's a sender problem. Check to see if the ground strap is installed correctly. It should bridge the rubber hose by connecting to the steel line on both sides. If that looks good, pull the sender wire and attach a jumper wire from the sender wire to ground. Turn the key to the "on" position and see if the gauge starts to come up. If it does, turn it off immediately so you don't burn out the gauge. The problem is in the sender or float. If the gauge doesn't come up, the problem is somewhere else.....gauge, voltage limiter, circuit board, wiring, etc.
Mark