This is the circuit.
If your tester is showing voltage at the fuse, my top suspect would be bad fuse (I've seen weird stuff like that before, fuse tests good but is actually bad under any load) or poor connection of the fuse in the fuse holder. It is possible to be somewhere along the grey wire, and if so the most likely place would be where the wire connects to the terminal inside the fuse panel or inside the connector. You can poke through the grey insulation with the tester to check voltage in the wire.