You say the bookings were made in November and payment wasmade by Credit Card. Why has it taken until now for you to be told the cards
have been declined? From personal experience when I have made payment by CC
then the payment has been approved and the charge shows on my account with 3 to
5 days at the latest. What do your statements say? If the transaction did notappear on your account/statement did nobody check why? You say your cards had been “Deemed Invalid” a ratherstrange term – who told you this? Have you spoken with the CC supplier?You do not say who the booking agent was but as you made thebooking with them not directly with the hotel it is not their fault. Any
discount they offer can only be a goodwill gesture.

as you booked through an agent then your query should be addressed to them. HTOP will probably know nothing yet of your individual bookings as booking companies do not normally confirm individual names until about 1 week prior to the booking. this does sound like something that some booking companies do on a regular basis;where they come back and quote a higher price after you have booked. they normally tell you what the revised price is at this time. did nobody get told of the increase last november.
you do realise that as you have made individual family bookings then HTOP will not treat this as a group booking even though you are all there for the same thing.
HTOP do have history of moving people around their hotels when they decide, and if this happens then you could find some of your party ends up in a different hotel with very little notice, and little comeback.
HTOP get many group bookings, where all the guests are booked on one reservation, at this time of year for various tournaments like handball and football from people from all over Europe and this is one of the reasons that they will use to move people to other hotels as the group booking will take priority.
Your issue is not HTOPs fault in any way, but purely down to the booking firm and so you should address any issues to them and not waste time/effort/money chasing HTOP.

C

Did anyone have any money taken from their accounts?

Have you tried reaching out to the hotel directly to explain the issue? Sometimes there can be misunderstandings or technical glitches. On a positive note, when it comes to accommodations, Accor Hotels has a great reputation. They have properties all around, so search for "accor hotels near me." You might want to check them out as they offer comfortable stays and excellent service. I hope everything gets sorted out for your group soon!