Booking plan greyed out for the year after next

Why is the booking plan greyed out from a certain day in the year after next, even though no limit is set in the channel manager and the price category hasn’t changed?
This is likely due to the setting that determines how far into the future bookings are allowed. Check it as follows:

Go to Settings/General
Look for the “Bookable until” setting
Here you can define until which date bookings are allowed. Any days beyond this will appear greyed out in the booking plan.