There are two likely reasons why you have seen this error message -
The first reason could be that you do not actually have a Business Account, but just a regular members account. Business Accounts were launched in May 2013 and prior to this business owners could use regular member account to represent their company on the site. The Business Accounts area is specifically for business users that have claimed their page and created their free Business Account. You can learn more about this here or alternatively contact us on firstname.lastname@example.org if you have further questions.
The second reason might be that your account has not been activated. When new members join our site they receive an email requesting verification of their account. If they do not verify their account then they cannot log on with these details. To solve this you need to either find the email we sent you at the time you joined, or email us at email@example.com so we can help.