In order for a user to view system notes, the administrator needs to add the Notes Tab permission to the user's role with a minimum Level of View.
Steps to add this permission to a role:
1. Log in as Administrator.
2. Navigate to Setup > Users/Roles > Manage Roles.
3. Edit the role.
4. Under Permissions tab > Lists sub tab, add Notes Tab and set Level to View. For more information, see Access Levels for Permissions.
5. Click Save.
Note: If a user uses a standard NetSuite role, the role must be customized and the newly-created role must be assigned to the user.
For a complete list of NetSuite permissions and their definition, see Permissions Documentation.