If a contractor is having an issue logging in, please check the following BEFORE logging a client ticket:
Are they active, you can view that on the contractor search page by searching by ACTIVE contractors only.
Is their email address correct?
This is critical because the contractor uses their email address to login and also to reset their password and if the email address is not correct, they can not login.
Make sure there are no spaces before or after the email address.
If everything is correct on your client side and the contractor still can not login, create a new client ticket for support.