Hey there, sorry for the trouble!

I don’t speak Japanese, so I’m going to reply in English. I hope that’s ok. If you would prefer to get help in Japanese, I can also loop in one of my fellow community team members to assist.

That said, I took a peek at your account on the backend, and it looks like you created your account on August 25th.

It is expected that new users, who created their accounts after June 2024, will not be able to see the option to “Go back to previous UI”.

You can check out the Help Center article here for more information.