The Nebelwerfer Operations Card states that it is used before the start of the action phase. It is purchased during the Command phase. So my question is:
1. Card is purchased during the Command Phase for 4 command.
2. Card is now active for the German player.
3. After the game round is advanced, but before the Action Phase begins, the German player attempts to establish contact with the Nebelwerfer, but fails to establish contact.
4. Can the German player attempt to establish contact with the Nebelwerfer during the action phase as an action, or does he have to wait until the next game round, before the Action Phase to attempt to establish contact contact again on the activated card?
For standard artillery cards, you can keep trying to establish contact as an action during each turn of your action phase.
No, for standard artillery cards you can only try once per round as well.
P41 rule book: Once during every subsequent round, as an action, the player can again try to establish contact.
So for the Nebelwerfer as well: wait till the next round.