First, welcome to Flyertalk.

Second, on results webpage for the "check rates and availability" search, look at the bottom of that page. There should be a box with a couple of links in it. One will be a link to 'View alternate locations'. The other will be a link to to a "dates flexible" webpage. From there, you can search for up to 4 weeks at a time to see if there are any days where the rate is available.

I just did that search and found your rate was only available on July 27th and July 28th (at least for the month of July.) I didn't search anything beyond that. So it is available, but just not that often.