If you are already logged in on 7 devices, it means you have exceeded the limit of shared devices. To resolve this issue, you need to remove logged in devices. Let us show you how: 

1. Open the Moon Invoice application on your device or tap on this link.
2. Go to My Account → Your Devices.
3. Review the list of your logged-in devices.
4. Click the ‘Remove’ button next to any device you wish to log out.

                                                                                                                                 - Moon Invoice