[QNAP- App Center] App Default volume does not exist. Please go to "Storage Manager" to create a new volume before installing apps.

I receive this error while trying to install a new app on my QNAP.

[App Center] App Default volume does not exist. Please go to "Storage Manager" to create a new volume before installing apps.

How to fix it:

1. Go to QNAP GUI > Control Panel > Privilege Settings

2. Privilege > Shared Folders and click [Restore Default Shared Folders].

3. Reboot Qnap > Try Install App Again > Enjoy > Done