Gauge issues?

The ground for the sender is a little metal strap snapped on the fuel line over the rubber hose there. There is a pic of that jumper in several similar threads. It could be missing or rusted enough to prevent continuity.
If you prove that sender ground is good the sender is definitely the fault. If the senders float was filled with fuel the gauge needle would at least climb from its home position to the empty mark at switch on.
Hope this helps and next time start your own thread rather than hijack someone elses.