You can call the regular number, or the PLT line if you've matched status. But Marriott does not have the "room available = award available" policy of Starwood.

No blackouts just means that at least one room was available as an award at some point. If the available award rooms are gone, they're gone.

As rooms look to start at $700+ for a lowest-level Garden room, 3x the typical rate, the odds of award inventory freeing up is pretty small, IMHO.