I works for me now. Thanks.

• Opened https://paws.wmflabs.org
• Signed in with Mediawiki credentials
• Granted the oauth permissions
• Clicked "Start My Server". It waited in https://paws.wmflabs.org/paws/hub/user/barcex/ until it timed out with a 500 error.

Just tried to create a user for myself and it fails. It keeps waiting on https://paws.wmflabs.org/paws/hub/user/barcex/ saying "Your server is starting up. You will be redirected automatically when it's ready for you" until it eventually times out.