You're not the only one as another member started a thread with the same issue.

Managed Payments is available in Australia and has been for a while now.

You're blocked because you would have received a message/s from Ebay not long ago asking you to register for MP and if you or any other sellers have ignored that request and time ran out for you to register then ebay are now blocking sellers from selling until they register.

And there must be a glitch because some sellers are now finding it difficult to register.

Best thing to do is go to the help section and type in managed payments and follow the prompts on how to register.