Ok, before getting on your sub, have you saved and quitted immediately when entering bunker at campaign start or chapter start? If not you must do it; quit and repeat. Do not overwrite save slots, do NOT use Autosaves.
If you click '2' on the left bar you should hear a voice 'Langsame Fahrt voraus' (= Slow Ahead) and your sub should start moving. If not, then post your problem and the picture link here to get a response from 'Vecko' the mod author:
http://www.subsim.com/radioroom/showthread.php?t=210703
[Edit]
Do you hear any sounds in the bunker?