Chances are decently high you haven't actually made an account at https://accounts.theorycraftgames.com/ - maybe you pre-registered (which is different from making an account) or you have a legacy steam account that isn't connected to our Theorycraft database.
EITHER WAY, try making an account with your email - if it lets you, then finish making your account. If it doesn't let you (ie. says "this email has already been used") then use the password reset functionality. Thanks!