Maybe you have a domain name that is in a non-English language (i.e., ริฟฟี่.ไทย). But there are many cloud providers and domain registrars that cannot accept this as a valid domain.
Most of the time you can solve this by converting your domain to ASCII format first, and using that as the value instead. This tool allows you to convert localized domain names to ASCII format (and it can also do the conversion the other way as well).
