Hi! I understand how frustrating it can be when you're trying to access important resources, especially with your GMAT coming up on Friday. It looks like the mba.com website is currently undergoing upgrades, which is why you're seeing the "temporarily unavailable" message.
These upgrades usually don't take too long. In the meantime, if you have an online GMAT exam scheduled during this time, you can still access your exam by clicking the "Launch Exam" button on their site.
Good luck with your exam!