I just discovered that I didn't renew my Premium Student discount and have been paying the full price of 10€ for the last 2 months.
When I'm trying to change my Subscription to Premium Student, Sheer ID verifications says that I've already used up my discount (which basically makes sense, since I already had Premium Student on that account, but just forgot to renew the subscription)
The student discount is only valid for 12 months at a time and it's possible that yours has expired - this can be the reason that you're being charged at the regular rate. No worries, you can easily reapply for another 12 months following the steps here.
If after this process you're still getting an error message, could you give these steps a try and see if they work for you?
Keep us posted.
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