@Amina-and-Kevin0
I can't offer much help - clearly as you say it must have been a serious complaint, which they are obliged to investigate, and I can understand in some cases why they would remove a listing.
Clearly for you it's a bit of a shock - hopefully once reviewed it will be in your favour. However, no matter what the outcome, you will not be told what the complaints was.
If it goes against you, then any future bookings would be invalidated, so I would start to think now about other listing sites ...good luck and I hope it's resolved in your favour.