A few days ago, I became as FCC supporter using Paypal, I’m glad for that, but still shows the pop-up window to donate. Why? It is annoying.
If I were you I’d feel free to take the privilege of using AdBlock to stop showing the ad 
I want to believe that the ad does not appear for those who have already donated.
FCC does not have a way to associate your FCC account and your PayPal donations. If you email team@freecodecamp.org with a copy of your transaction receipt and the email address associated with your FCC account, Quincy can manually update your account so that you don’t see the support requests. Please be patient. There are millions of us and one of him.