Error when uploading PEM file for https configuration

I have just finished installing the globaleaks internal site and need to configure https. I am trying to do this from the network settings area of the admin portal, but when uploading a PEM file to ‘Certificate (PEM)’, the error “Error on input validation []” is shown.

For context, the SSL certificate is currently stored in Azure in a pfx format. This is then converted into the required pem format using openssl.

Any suggestions on how to resolve this would be appreciated.