Unable to book either through the airline website or expedia, fare shows up on google flights though.
I was able to price it on priceline using bookwithmatrix. Can you try ITA then bookwithmatrix or powertools?
Apparently, you can pay a nominal fee for an upgrade to first when you check-in. If that's the case, I wonder if you get re-booked to F-fare class (ie. F or A) and subsequently earn miles.