Can I add a donate button to my organization's Facebook page?

This used to be possible. But Facebook has recently implemented a restriction on adding donate buttons to external donation pages. Now, nonprofits can only add a donate button to their Facebook page if they have signed up with Facebook Payments. 

If you use Facebook Payments to receive donations, you can still log these donations into your Donorbox dashboard. You can add them as manual donations. All your financial records will remain balanced. Donorbox does not charge any fees for adding manual donations and your donations totals will remain accurate.

You can still add links to your donation page in your Facebook posts. Please check out this solution to find that link to share with donors.