In the datasource configuration, in the "full path to private key", do you have the filename in that string?
I.e, if your private key file is file.txt
the path needs to be c:\directory\file.txt
Second - what format is the private key in? Is a putty formatted key? If yes, you want to convert it to OpenSSH format with PuttyGEN
Download puttygen, Load the existing key -> Conversion -> Export to OpenSSH