Stop sells can be placed in the Availability & Sell Method Calendar. These prevent room types from being sold on certain dates.
To remove a stop sell:
Go to the Availability & Sell Method Calendar.
Room types with a stop sell in place will be coloured red:
Ensure you have selected the "Set Sell Method - Long Term" button - it should be lit green.
Click on the first cell for the room type with the stop sell on it:
A small pop up window will open.
Select the room type (you can select more than one if needed)
Choose the date range to remove the stop sell from. If you would like to remove it indefinitely, click on the small infinity symbol on the right.
Click Inst. Confirm. It must be lit green.
Click Set Sell Method.
If the stop sell has been successfully removed, the cells will now be white.