Unable to use this private key file, Couldn’t load private key, Key is of wrong type

If you see one of these messages, it often indicates that you’ve tried to load a key of an inappropriate type into WinSCP.

You may have specified a key that’s inappropriate for the connection you’re making. The SSH-1 and SSH-2 protocols require different private key formats, and a SSH-1 key can’t be used for a SSH-2 connection.

Alternatively, you may have tried to load a key in a “foreign” format (OpenSSH or ssh.com), in which case you need to import it into PuTTY’s native format.1