If it were me, I'd contact Marriott, so the call/email is logged and they've given you a time estimate. And take screen shots of everything. Given the uncertain future, it may not help, but can't hurt to have an electronic paper trail. Most likely this all works itself out over time and you get your refund, but you never know. I believe Marriott is who you've done business with, not the individual property. I believe if a franchised property closes down, for example, Marriott is still responsible for refunds.