A change in the Maps.cfg file can affect whether the compass appears around the player u-boat. Specifically, the SymbolZoom setting which should equal 10.
Some mods, like OLC's GUI alter the Maps.cfg so SymbolZoom=1. This will cause the compass not to appear when you zoom in.
I'm fond of modding different mods & combining them, so I know the headaches this can cause.
