I reported this issue through Unreal Online Learning Support in October 2020. Kait P., the QA Lead Consultant of online learning, said that he had communicated this issue to the back-end developers, and said that could not find my account information after querying the back-end.
It seems that as long as the email is modified, the Epic Games account cannot be synchronized with the Online Learning background account management, resulting in account login failure and the page cannot be displayed normally. I can’t believe this problem has not been resolved after four months, which bothers me.