I cat't use cloudshell

I can't use cloudshell. I can't use it from root, and IAM user who gave full access to cloudshell can't use it either. Even if I change the region, I can't use it. Only shows following sentence.

Unable to create the environment. CloudShell にアクセスする前に、アカウントを確認する必要があります。アカウントを確認するには、AWS Support 。

Plesase solve it.