If you are using POSTrack 4.07J with Windows 10, the SMB 1.0 protocol must be enabled, otherwise you may encounter errors when importing a new flight plan.
To enable the SMB 1.0 protocol in Windows 10:

1. Open Control Panel
2. Navigate to Programs or Programs and Features
3. Click on Turn Windows features on or off
4. Scroll down to SMB 1.0/CIFS File Sharing Support
5. Click on the tick box on the left hand side, all three SMB features should have check marks next to them. Click OK.