is it for all OTAs or just a specific one? I had a similar issue not too long ago and it was booking.com only, I had to manually re-open the category in extranet. You will have to disconnect Mews to manually open them and then connect again if you’re using the integration. I did inform the support team before I disconnected so they knew there would be a request to re-connect and they could react quickly when it came. 

Thank you, I have managed to reslove, the room wasn’t mapped, although it doesn’t explain why it was able to be booked up to the end of the month. 

the open to end of month is because bookingcom works on last availability synced or updated, so if it was synced prior to mews, and then never mapped, it simply would have just kept the availability that was in at the time of being ‘unmapped’. If it was a new room type, booking creates the inventory based of number of rooms you enter on listing, for a few months ahead and just keeps at that….. its a nightmare for busy hotels as can cause a ton of overbooking