File Transfer to Bank

Hi. This is my first time posting so please be patient.

I am trying to transfer files from our ERP system to a bank using an authorise FTP server. I have generated a public and private key and sent the Public key to the bank as requested.
I am now trying to send a file to the bank using the details they requested. When using PSCP.exe and specifying the private key file I get the error "pscp unable to use key file (unable to open file)". However when I load the key into Pageant or use the Winscp GUI it works and I am successfully connected.
The reason why I want to use PSCP is because I want to create a scheduled task that will run periodically to send any files in a certain directory but don't want the server it runs on to be logged on.

Can someone please help with this?

We do not provide support for PSCP. That has nothing to with WinSCP. Though if WinSCP can use the key, PSCP should be able to use it too.

Anyway, WinSCP supports automation too and can be scheduled as well.
See https://winscp.net/eng/docs/guide_schedule