Can't connect to MyCloud via Windows Explorer or Windows Backup

Hello,
I wanted to back up my PC to my MyCloud using the Windows build-in Backup Function. I followed the steps in the manual but couldn’t select my MyCloud as the Destination. When I wanted to select a Folder on the MyCloud Network Storage it showed a window just like this. I tried my normal MyCloud credentials, but it didn’t work (I also tried adding a backslash to the front of the username, so it woudn’t use a domain), but it didn’t work. Same thing happens when I try to access the MyCloud from the Windows Explorer.
What did I do wrong?
Thanks for your answers

What Windows OS are you using? Why don’t you upload your screen capture so it shows in your post?

cat0w
USA

What version of Windows do you have? Microsoft Backup and Restore does not support backing up to NAS devices on certain versions of Windows; like Windows 7 Home Premium. Windows 7 Ultimate and above apparently support NAS backup using Microsoft Backup and Restore.

There are several free basic backup programs one can use instead. These include the WD Smartware program included with the My Cloud, to using free 3rd party programs like EaseUS Backup (http://www.todo-backup.com/products/home/free-backup-software.htm).

I use Windows 7 Professional.
Thank you for the advice with the advice with 3rd party programs, but I have good experiences with the build-in function so i’d rather stick with that