I wouldn't help until at least 40 hours after first pip. Ducklings can take a little longer than chickens, so don't worry too much yet. Just watch and make sure you still hear knocking every once in a while, and doesn't look distressed. I just had 2 take over 40 hours, so I feel your pain. lol
so I fear it could have an infection and it's probably dehydrated.
Saturday, the kids are home so there will be extra eyes peeking in on them all day and any sign of trouble would be noticed and reported! They might come up with questions I haven't thought of yet so be warned;-)