Possible problems

Note: You can check most common cases for domain configuration in our Guide
I see only "Applying changes. Please wait..." or "Unable to get domain info. Try again later." and no settings. 
Just wait 6-12 hours so our system can process your request. If you still see this message after 12 hours of waiting, just let us know by mail and we will solve the issue as soon as possible.
I see error message "Domain is not valid." after applying my settings.
Double check if your domain is valid. You can try to use some online tools to do that. For example: https://www.whatsmydns.net/
I see error message "Domain is already used." after applying my settings.
In this case the domain you've chosen is already taken by some other customer. You have to specify another one.
I see error message "Certificate can not be recognized." or "CA bundle can not be recognized." after applying my settings.
It is not possible to parse the certificate you inserted in your custom certificate/CA bundle textbox. Both of them have to be valid x509 certificates.
I see error message "No key entry was found for this account. Please generate CSR first." after applying my settings.
Generate and download your CSR first. Just click on "Generate" link in your "Hosted Account" screen of Domain settings. Then you can setup other custom certificate settings.
I see error message "Unable to check domain. Check if it is valid second or third-level domain." after applying my settings.
It was not possible to dig the domain you entered. It is not pointed to our srevers and/or your hosted account. Double check you custom domain DNS settings.
I see error message "You can not use default certificate for custom domain! Please choose custom certificate." after applying my settings.
This is not allowed configuration. You can use only your custom certificate for your custom domain. It is technically impossible to use the default certificate. It is suitable only for domains ending with .postafiliatepro.com
I see error message "Certificate and private key do not match" after applying my settings.
In this case you have a wrong certificate generated by another CSR. Generate a new CSR and use it for your certificate creation.

I see error message "Certificate chain incomplete" after applying my settings.
It means that the intermediate certificate (CA bundle) was not added along with the main one. You need to add the CA bundle certificate in the same field with the main certificate right below it.