Upgrade from Photography Plan to Teacher All CC Apps Plan

I've updated the email address on my account to a teachers email, verified the new email and gone through secondary verification via a code sent to my phone then attempted to buy the CC all apps through Teacher/Student app. However, the payment box is greyed out and when I've gone through to my account, as prompted, to choose to upgrade the plan it's not visible to select. The plan is advertised as £16.24 per month but it does not appear in the options to switch to another plan. Screenshots below. Is there something I'm missing in terms of verifying or making the Teacher plan available through my account or is this an issue with the website?