When the system refuses

That room is already occupied for those dates

Somebody else is in it for at least one night of the range. There is no override.

The room you chose already has a booking overlapping those dates — often by a single night at one end, which is why it looks free on a quick glance at the chart.

There is no override. The database refuses to hold two bookings in one room at once, and that refusal is what makes the chart trustworthy.
Look at the chart for that room across the whole range, not just the arrival date.
Either pick another room of the same type, move the other booking, or split the stay across two rooms and tell the guest.

If the chart looks empty for that room and it still refuses, check the month either side — a stay running over the month boundary is easy to miss.

More in When the system refuses

It refused. Start here.How to read a refusal, and the three kinds this system gives. The room is vacant-dirtyHousekeeping has not released it. A manager may override, and housekeeping is told. The folio carries an outstanding balanceCheck-out refused because money is owed. Three legitimate answers, all recorded. Cannot amend: minimum stay, maximum stay, closed, stop sellThe dates you asked for hit a restriction on the rate plan. A manager may override. Cannot move, and the administrator overrideRoom moves refuse for four reasons. Two can be overridden and two cannot. The rate comes from somewhere you cannot type overA contract or a channel set this price. That is the system protecting an agreement. A reason is requiredCancellations, voids, comps, overrides and moves all need one, and it comes from a list. Day end will not close the dayEither the day has not happened yet, or a shift is still open. That module is not part of this subscriptionThe hotel group does not hold that module. Only Asar can switch one on. That link is not liveOne sentence for three cases: unknown, already used, and lapsed. Wrong hotel ID, username or passwordOne sentence for all three, and the one people actually get wrong is the hotel ID. The Aadhaar or PAN is not validA format check at the desk, not a lookup against any government service. It needs a company or an agent firstA booking billed to somebody else needs that somebody on file. The dish, category or outlet will not saveEvery one of these is a field the form needs and does not have.