Hi @Page33
Date availability for custom promotions is decided by Airbnb. This is why the dates are greyed out on your calendar. See help article below:
Why Can't I Set a Custom Promotion?
https://www.airbnb.com/help/article/2719
If the dates are not available for a custom promotion, you can always just reduce your prices manually. By reducing your prices, you should show higher in search results as price is a key factor in the Airbnb search algorithm.
Min Night Stay
Another thing to consider is your 7-night minimum. This could also be hurting you in search results. The less availability you have the lower you will appear in search results. Additionally, if a guest is searching for less than a 7 night stay, your property will not even appear and subsequently less bookings. You might consider lowering your min stay to 4-5 nights; especially as the season winds down.