If you paid with PayPal, check your account email. It can take a few minutes to show. If you paid with CoinPayments, check the email you specified.
We recommend you read the rest of the FAQ before creating a ticket, as it explains common user issues. You may create a ticket by clicking the button on the order page or in the email you received.
To gain full access to the account, you must migrate it to your email. You may do so here. UFA accounts come in username:email:password form. Enter the details in the first half of the form and then enter your email in the second half of the form. Once you have migrated the account, check your email for a confirmation link from Mojang and then click it. From there you can reset your password here. If you encounter an issue, please create a ticket.
This is a very common user issue. Do not try to login to OptiFine's website directly, it will not work. If you want to move the cape, download the latest OptiFine jar. Login to your account on the Minecraft launcher and launch the latest OptiFine version. Once you have done that, go into settings -> skin customization -> OptiFine cape -> open cape editor. This will open a link in your browser where you can move the cape to your account or customize it however you'd like. An in-depth guide can be found on OptiFine's website here.
This is another very common user issue. If you are using a checker or cracker, please be sure you are using proxies that are high quality. We recommend RSocks. Not using proxies results in Mojang banning your IP because of too many logins with the same IP. This causes Mojang to mark all of your accounts as invalid.