Yes, I followed that process already today. I added in the correct information that I needed to, but I am still getting errors. I just now tried to send another test and its still not working.
I've gone in and added her MailGun information into the 'passwords' area. If you can, could you please login to her mailgun account and double check for yourself that I've been doing this all correctly? Once again, the website's ID is c2469.