Worldwide testing helped British magnetic torpedoes work

Did any navy make magnetic torpedo detonators work during the Second World War?

Yes. The Royal Navy began with working Duplex torpedoes in part because it had tested them across the differing magnetic conditions of a global operating area.

Several navies eventually made magnetic pistols work, but many suffered serious early-war failures. Local magnetic fields vary by region, so a weapon calibrated in one area may behave differently elsewhere. The Royal Navy's regular worldwide operations provided more environments in which to expose and correct those faults. That extensive testing allowed British Duplex torpedoes to enter the war in a more reliable state.