Why did you cancel your subscription? The student price would have kicked in automatically on the next due date. The Boku payment option is ony available when an account is created and not for renewals so this is likely to be the issue. If you get in touch with the helpdesk, they may be able to help.
If you get an automated response directing you back to the community or to the help pages, make sure to reply to it directly to speed things along.