Serperior's Versailles

I'm trying to do my login registration in a MMORPG and it keeps saying a password must be ''between 6-16 character, at least one number, and no apostraphes''

I'm going to give you a generic version of the password I'm trying to input: x56y74m98, which is 9 characters long, contains 6 numbers and no apostrophes, so, why does is it telling me it's unnacceptable?