Apple Music is not letting me change to Student subscription.

Hi livia95,

It may be unrelated but try disabling Low Power Mode, then try again. Low Power Mode helps your iPhone battery last longer but some tasks might not work properly as mentioned in Use Low Power Mode to save battery life on your iPhone or iPad - Apple Support.

If the same continues and you have another device available, try to sign up for the Apple Music Student subscription there. Does the same occur?

Are you switching from a previous Apple Music subscription? If so, steps may be a bit different. Try the following steps from Get an Apple Music student subscription - Apple Support.

"In Settings on your iPhone, iPad, or iPod touch

1. Go to Settings > [your name], then tap Subscriptions.
2. Tap Apple Music Membership.
3. Tap "Verify your student status." You'll be redirected to the UNiDAYS website.
4. Follow the prompts to verify your eligibility. If the verification is successful, you'll automatically return to Apple Music and continue your Apple Music student subscription."

Have a great day!

Hello livia95,

Thanks for posting in Apple Support Communities. We understand that you're not able to sign up for an Apple Music student subscription.

Be sure you're completing the following steps: Get an Apple Music student subscription

If you continue to experience the issue same issue, these steps may help:

1. Quit and reopen an app on iPhone
2. Restart your iPhone
3. Update iOS on iPhone

Let us know if this helps.

Take care!