I tried to buy data plan from Rakuten Mobile

Hello, I'm currently on a long term stay in Japan and would like to buy a Japan phone number. And I chose Rakuten specifically for its cheap plan compared to others. However when I tried to apply for it, I couldn't get pass the personal details page (Step 1) and it kept saying that they can't connect to the Rakuten system. Any idea how to deal with this? Is it really the system or something I had to do on my behalf?

by EasyChampionship9073