Had student discount for a year, and now cannot renew discount

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I am still a student at a university that gives the student discount. However, when I try to sign up for the subscription now, it gives me the error:

"Unable to change plans. This could be because you're not eligible for this plan, you're already on it, or you don't have a stored payment method."

This is especially irritating to me and I am considering of switching off of Spotify if this cannot be solved. Help?