I'm Demanding Stayforlong Confirm Our Reservation Before Our Trip Begins

We made a hotel reservation through Stayforlong on June 16th and are planning to check in on July 3rd. $1,581 was charged from our credit card, and a confirmation email was also sent to us. However, when we called the hotel, they told us no such reservation appears in their system.
The hotel is currently stating that they're trying to contact the intermediary agency, but they haven't been able to get a clear answer from them either. We can only communicate with Stayforlong via email, and the responses we receive are both insufficient and unconvincing — the problem is not being clearly resolved.
I am requesting that this reservation, which we've already paid for, be made visible in the hotel's system, and that our reservation be immediately and definitively confirmed so that our stay can take place without any problems.