Guests do not response to any message, what if they do not arrive

If they will not arrive and you are not possible to charge them, then you will loss money because you will probably not sell the room to others. Booking com has no any help or responsibility for that. We operate hotel in India and started to hold rooms after the advance only. Otherwise it is always a risk, and here even with the advance sometimes they do not come 🤷

I think in this case you have the right to sell the room to other people and you have a clear reason for that