Scenario: A user is in the process of installing NetSuite for Outlook but receives an error message on the login page "Invalid Login. Customer access is disabled."
The solutions is to add a permission called 'Web Services' to the users role, not as a Global Permission.
1. Navigate to Setup > Users/Roles > Manage Roles.
2. Edit the role in question.
3. Go to Permissions > Setup.
4. Add 'Web Services' then set to 'Full'.
5. Click Save.