Student reduction decreases the second year. That is normal. Why it did not happen to you after the first year, I do have no idea. Maybe it was a special 2 years reduction.
If you want to clarify the situation, you can always contact Adobe customer service on account and payement issues. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. If the chat window fails to open, or is non-responsive, use a different device to start the interaction.