In this specific situation, the CAA has provided details of what to do at https://thomascook.caa.co.uk/customers/if-you-are-currently-abroad/managing-difficulties-with-your-accommodation/
In short, they advise not to pay anything unless their team specifically advises this in your personal circumstances. Ordinarily the accommodation providers would be expected to accept the CAA's guarantee, which should be far more reliable than Thomas Cook's guarantee that the providers were previously happily accepting.
Whether the contact number provided on that page is adequately staffed is another matter of course.
In general, the advice would be to contact whoever it is that you expect to be paying the hotel on your behalf (e.g. the travel agent who made the arrangements if they're still trading, an insurance provider, or similar, or in this case the CAA), in order to clarify why the hotel isn't accepting their payment or guarantee.
The original documentation providing details of the package, guarantees, insurance, etc. would also certainly have details of relevant emergency assistance numbers, so one can best prepare for unexpected situations like these by ensuring the relevant documentation is printed off and kept to hand.