This original thread was from the Hyatt partnership, but now that Hilton is SLH partner - I have a similar issue to the OP.

Looking at a SLH property in July for a 5 night points stay. My exact dates, Hilton shows the entire hotel as "sold out" (that is for cash and points). The hotel's own website shows it as available with multiple room types for all 5 nights. I checked the Hilton website using flexible dates and it appears the last night of my stay is the problem, on Hilton's end. The first 4 nights are available on points and cash. Weirdly, it's a Monday night that is the problem, so not weekend nights that the hotel is holding inventory back.

Any chance the Diamond desk could access that inventory to book it for me, using points? I wouldn't think I could book directly with the hotel and use points... Hilton shows plenty of nights available via points at this hotel in July, it just happens to not for one of the nights I need.