In certain configurations of Salesforce, some users may experience the following error on the NetDocuments login screen.
Error encountered during login: 5 INVALID_SESSION_ID: Invalid Session ID found in SessionHeader: Illegal Session Visit our support page for help.
If you receive this, you may be able to resolve it by logging in to your Salesforce account and going to Setup > Administration Setup > Security Controls. Then click "Session Settings" and uncheck the box for "Lock sessions to the IP address from which they originated" then log out and log back in to Salesforce. When you go to NetDocuments for the first time within Salesforce, you will need to put in your username and password to reconfigure the single sign-on.
This can also be caused if multiple users are logging in to the same Salesforce account.