You can always grab an Invoice (if you have a balance) or a Receipt (if you're full paid) for participation with Underdog.
Just log in to your Player Page, and click the link in the status window:
Feel free to try again, and be sure to grant the requested privileges.
These are the accounts with the same email address as your Facebook account ().
If you want to use a different account, log into that account using your password and link your Facebook account from your Player Page.