Hi there, sindile_x.
I see that you're trying to subscribe to an Apple Music Student subscription. The issue is, your school doesn't provide a student email address. So, your email isn't accepted and approved by UNiDAYS, and I'm happy to help.
Get an Apple Music Student subscription -- Review the information provided in this article. Since UNiDAYS validates your enrollment in a degree-granting university or college, you will need to contact them for support. Please see below:
When you join Apple Music as a student, UNiDAYS, a student validation service, confirms that you're enrolled in a degree-granting university or college1.
Periodically, UNiDAYS re-validates your student status. If UNiDAYS finds that you're no longer a student or if you have a Student subscription for a full 48 months, your subscription automatically becomes an Apple Music Individual subscription.
And
If you need help with your UNiDAYS account, contact UNiDAYS Support.
1 To qualify for an Apple Music Student Membership, you must be a student studying a bachelor degree, post-graduate degree, or equivalent Higher Education course at a University, College (US only) or Post-Secondary School (Canada only). Junior, technical colleges, and special courses are also eligible in Japan.
Take care, and enjoy your day!