Hotel herrnschlösschen in Rothenberg ob Tauber

How did you book the reservation? I have had success using What's App to email European businesses. Good luck!

I booked it online but there was a mixup.

Good idea. I tried calling directly and emailing them. I'll try WhatsApp. Thanks!

It says you can cancel up to 5 days before your stay. It looks like they reserve by an email type system. I would keep sending an email through their contact page everyday until they respond. Give them several days. If you don't hear from them, cancel and stay elsewhere. Document your cancellation for your credit card company in case they charge you. There are too many alternative places to stay. You don't have to put up with poor communications.

I have had a lot of communication problems with good European hotels, with great reviews. Once I arrive, they seem to have been equally frustrated communicating with me.
Sometimes the hotels do close down in the off-season, and when they are closed, they do not communicate, unlike Americans, who are always connected, it seems.
For whatever reason, What's App does work better, and I think it's cheaper for Europeans to use.
Good luck!

when you called (I presume during German working hours?) did they not answer the phone or did you not get anywhere once they did answer the phone?

what does "They have been of no assistance whatsoever" exactly mean? What did you ask and what was the reply?