Nope, hotel is not allowed to limit access, all Golds and Plats are entitled to access the lounge regardless of rate. Claim the $100 guarantee and if they refuse call the plat line. Get your $100 and lounge access fir the remainder if your stay.

Looking at the Autograph Seoul thread (where you’ve cross-posted this issue, naughty!) there are posts that the lounge is dreadfully overcrowded and does not seem to have been allocated the space for the numbers it’s seeing. No doubt you are a casualty of its attempts to deal with the problem, but that doesn’t make them right.