You must verify ownership of this certificate’s domain(s)in order to upload it

I received the above error, time and time again while trying to update the SSL certificate for one of my Appengine projects.

Despite the fact that I had

1. Already verified both the root and www. domain
2. Updated this very SSL certificate and domain several times in the past

Solution

Turns out for whatever reason, Google now requires you to also verify ownership in Google Webmaster Tools (Make sure you are using the same Google account to do this). I didn’t see this mentioned anywhere in the console.

Thanks to the users at this Google groups post for pointing me in the right direction.