As I understand it provided you are logged in to your Accor account with Platinum status an availability guarantee rate should always be offered until 48 hours out form checkin (unless it is one of the few blackout dates). The rate should show as "Le Club AH loyalty platinum" or similar. That was my experience of using availability guarentee last week.

When not logged in to your Accor account the hotel will simply show as unavailable.

If whilst logged in no rates are being offered it is either a IT glitch or the hotel concerned is possibly rather naughtily ignoring this stated status benefit.

A Accor hotel choosing to ignore a stated Le Club benefit isn't beyond the realms of possibility?