Student email is already in use

Adding st-email:
Tried to add my student email ,under Add email address on my other [non-student] github account,
but when I do i get Error adding [st-email]: email is already in use

Create account with st-email:
Then I tried creating an account using the [st-email] but Email is invalid or already taken pops up

Reset password:
Tried to reset the password of the [st-email] but That address is either invalid, not a verified primary email or is not associated with a personal user account. Organization billing emails are only for notifications pops up

btw I’m still a student and my uni is listed as an option on GitHub student pack, also I’ve used github since mid 2020.

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