If you are already Platinum, you should have been gifted 25 nights. So you are 25 nights short. I don't think that Marriott is inclined to do anything extra, especially if the hotels in Australia are actually open. Marriott consistently sent emails to UK-based members in the early part of the year, suggesting local getaways when in fact Brits were also locked down and couldn't even legally check into hotels. So they are also completely deaf to non-USA issues...

You might be able to do a Platinum challenge in 2022 or beyond to recover your status though.