You by passed the GFI
If you are not tripping the circuit breaker
You do not have a short
You have an open circuit
GFI trips because of an imbalance of electrical current
More amps on the hot wire than in the neutral wire
Meaning power is going to ground thru another path
The tech should remove all outlets, and read continuity on the neutral white wire between boxes
If the GFI is tripping with all other outlets removed
Remove GFI and check continuity between breaker box neutral and GFI neutral
No shore power, generator, or INVERTER
While doing continuity checks