Open it back up and try turning the pot by hand. Turn it all the way up to the toe end and then turn it down slowly and see how far down you have to go before you hear a change.
IDK for sure what's happening here, but I know that some of these wah pots have a kind of S shaped taper such that nothing really changes at the ends of the rotation. It's also theoretically possible that there's just a certain point in the circuit itself where increasing (or reducing, whatever...) the resistance of that pot just won't make a difference because it's already hit some sort of limit.
Either way, though, if you figure out how far up you can turn it before it stops making a difference, and set it up so that it gets just there at full toe-down, you've got all the treble you're going to get without changing components.