How to solve "impossible to initialize SFTP protocol" issue ?

Hi.
I'm triyng to access an mPower ubiquiti device via WinScp.
I can access the device via Putty but not via WinScp.
In this case I receive the error attached (impossible to initialize SFTP protocol).
Any idea?
Thanks in advance

It looks like the device does not support SFTP. Do you have any reason to believe it should? Can you connect with any other SFTP client? Did you try SCP?