Trying to sign up for premium with NUS extra card but can't

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So I have been trying to sign up to spotify premium using my nus extra card, but can't get past past this step despite entering all the correct details: https://www.spotify.com/uk/nus/go/

When I click Submit it stays on the same page.

Surprise surprise my message to spotify customer support went unanswered.

Could you sort it out please guys, I'm using an account that I have had for some time, and have had premium on in the past.

Also, will i only be able to use this discount for one 12 month period, or when I get my next year's NUS extra card, can i do the same thing again?