Hi Zu wang,
It looks like you did not provide module access to the user roles. Please check the above process and check
Create a user role – Eg Customer
Click on the edit and provide the access to the Customer user role to any of the module
Hope it helps!
This option is only enabled when the app status is Incomplete. You will need to go to the individual modules to change the security. Could be an idea (you can post it) to give an overview of the status per module and let you link to the individual modules.