Another gas gauge issue

Might be a dozen clips attaching the hard fuel line to the chassis. No doubt about chassis ground path there when the vehicle was new. Somewhat difficult to believe it would fail completely but... enough resistance to prevent sender function is witnessed. There have been similar threads, fuel gauge comes and goes with weather/rain.
One remaining question... Did you reuse the original seal at senders mounting? I can't say "I know it will leak." Every one I've removed showed enough deformity that I expected it would leak.