Hi Paul,
Generally, any non-profit organization can apply for Office 365 non-profit service with the steps below:
1. Sign up for an Office 365 for Non-profit trial account in the following article:
office.microsoft.com/.../compare-office-365-for-nonprofits-plans-FX104081605.aspx
2. Verify the organization domain in the account.
3. After that, our related team will do further validation.
If the charity is validated, they will receive an automated email of approval and will see the nonprofit subscriptions available for purchase in MOP.
Given this situation, I’d like to know if you have tried the steps above. If you have tried these steps but still can’t apply for it, I’d like to recommend you contact our sales and billing team for more professional help on this issue. They will help you check the detailed information about your tenant at the back end. Thanks for your understanding.
Best Regards,
Richard Ji