Resolve CSR to PEM Issue

I’m finalising an MDM solution and the last step is converting my certificate signing request into the .pem file the system expects. On macOS I create the .csr with a GUI app, yet when I feed that file into the conversion process I consistently get “File access denied”.

I need you to:
• diagnose why this particular .csr is being rejected,
• successfully generate the required .pem, and
• show me the repeatable steps (or correct settings/permissions) so I can recreate the file myself when the certificate renews.

If you prefer using Terminal-based OpenSSL or have another reliable workflow, that’s fine as long as the end result is a valid .pem that my MDM server accepts. Quick turnaround is appreciated; as soon as the file works I’ll release payment.