Here are the common problems when you try to build your site and what to do about it:

“…is not a valid name for a website. You can use letters (abc), numbers (123) and dashes/hyphens (—). Spaces are not allowed and the domain can't begin or end with a dash.”

These are the rules when trying to buy or setup a domain name. The internet registry doesn't allow certain sets of numbers or symbols in domain names.

The username already exists tied to a different email account. Either choose a different username or use the same email it was originally used with.