Instant Book Oddity: Only shows for certain dates. Help Please

I have Instant Book tuned on with only the recommended requirements and no additional requirements are checked. When I do a search for my property I can only see the Instant book icon if I enter a search of 14 nights or under. As soon as I enter a longer stay, the Instant Book option disappears! Similarly, in my listing the book button changes to “request to book”. What gives?

I really would like my guests to have the option to Instant Book for longer and monthly stays. Right now I have a 10 day minimum, and a special rule for a 5 days in March. (I am a superhost)

Have you called Airbnb about this?

I tweeted the support, still waiting for reply.