Your booking site calendar shows availability for the next 12 months, even though your PMS booking window is set for 18 months, 2 years, or longer.
Why this happens. HomeRunner syncs a set number of days of calendar data per property. The default horizon is 365 days, so the site calendar stops at 12 months regardless of the booking window in your PMS.
What you can do. If you actively take reservations further out, contact support to have the site calendar horizon extended to match your configured booking window and a full calendar resync run. After the resync, those far-out dates become selectable on your site.