Please refer to the following list of instructions for troubleshooting:
1. Make sure that the LAN port, which is connected with the setup PC, and the WAN port, which is connected to the network domain of the PC whose folder you're backing up, need to be connected at the same time, meaning you cannot complete backup settings with just one computer. (See 2-1 in the User's Manual.)
2. Please check the IP of the computer whose folder you're backing up by entering "ipconfig" in Command Prompt (cmd). As pic below shows, the IPv4 Address is your IP address. Here, for example, it is 10.16.1.99.
3. Check the User's name for the computer whose folder you're backing up by entering "whoami" in Command Prompt (cmd). In the below picture, for example, the User's name will be "test".
4. Before backing up folders, you need to modify the permission settings for "Sharing". Please first enter "Advanced Sharing", and set the access permissions for "Everyone".
5. If you are running Windows 10, please make sure that all checkboxes in the following path are selected: C:→Windows→System32→OptionalFeatures→SMB 1.0/CIFS File Sharing Support
If you run an OS prior to Windows 10, please skip this step.