Interesting. Thank you so much, will have a look into this.The float for the gauge is tangled. It happened to me when I installed the Fore Innovations fuel system. The gauge didn't work, took the fuel hat out and the float was caught on the plumbing inside the tank.
If it's not caught on anything, the float arm could be damaged or the hinge rusted. You'll have to look inside again.
Here is a picture.
Tangled
Untitled by jpjr50, on Flickr
Correct
Untitled by jpjr50, on Flickr