@lparker I found this: Error with cert-issuer
That person solved a problem with the same error, using the plain text unencrypted format of the private key. The same format I have also used.
Like this: b5d9ce34e5e01bb136760ffdda4b3f5769665fddedd5cdb0edddfe208ed01e29 (just an example)
Just to confirm, is that the correct format?
Thanks