GitHub student email registration is not available

There is a problem with「Get your GitHub student benefits」.
At [What e-mail address do you use for school?], I cannot press the [add an email address] button.
Isn’t it displayed if there is no school email registration ( on the linked account?
My github account has a primary email address and a backup email address respectively.
I don’t know why you can’t make a choice, but if you can’t make a choice, you can’t proceed with the application.
I am waiting for your answer.

Hi there! Thank you for your message. Please post this in our GitHub Education forum and the friendly folks from the education team will be able to help you.