Torpedoes not exploding.

[Bakkels]

Or you are waiting for the external torpedoes to load. Which will not happen. You have got to drag them to the internal torpedo slot first. (I hardly ever played the type II so I don't know if they have external torpedoes?)

Otherwise, as someone else said, be sure to have enough (and not too tired) crew in your torpedo room. The better and less tired your crew, the faster your torpedoes load.