Renewing student confirmation for Apple Music subscription

Re: "Apple Music Student Subscribe : I can’t renew my student confirmation in the web site, how can I renew it to benefit the offer for students?"

Seems you just need to provide proof of your current student status:

See if Apple Support's online linked article can help: Get an Apple Music student subscription - Apple Support

Eg:says:

"How to re-verify your student status

Once a year, you will receive an email when you need to reverify your student subscription.

You can reverify your student status in the Apple Music app on your Mac or PC.

You can also re-verify in Settings on your iPhone or iPad."

and

"Re-verify your student status in Settings on your iPhone or iPad"

1. Go to Settings > [your name] > Subscriptions. 
2. Tap Apple Music.
3. Tap Verify Student Status. Need help?
4. Follow the onscreen steps to verify that you’re a student.
5. If the verification is successful, you’ll see a confirmation screen."