customer is using the correct login information, but gets an error
and can't login: 'Unfortunately the information you entered is not
correct. Please re-enter your information and try again.'"
they are actually using an incorrect password. Try resetting their
password. See Sites > Site Users. If this is a B2B storefront,
make sure the User is Approved. See Sites > Site Users. The "User
Account is Approved" box must be checked.