"Rocket League" is one of the most competitive games on the market. Although countless players hope to climb the ranking ladder of the game, some people may just want to expand their cosmetics collection like a real collector. Although you cannot fix this problem manually, you can go through a few steps to see when the website can be restored.
During the maintenance period, you should be able to get the estimated time of arrival of the fix from the social media channels of the Rocket League Garage. If there is an ongoing server problem that the developer also reported on Twitter, you need to wait for the website to come back online.
If you keep seeing a blank screen and no news, you can try a different internet connection to exclude the one you are using. Using mobile phones and cellular data plans will be the fastest way to resolve home network failures.
If you can use your cellular data to access Rocket League, you can try to reset your router or change your DNS, which can help you return to the site when you know it is still online.