The TLS connection for energy drivers / Process Gateways, or the TLS connection for the zenon network, fails with a specific error log message

The TLS connection for energy drivers / Process Gateways, or the TLS connection for the zenon network, fails with a specific error log message

Attempting to establish a TLS connection using one of the energy drivers or Process Gateways or using TLS for the zenon network, fails. The following error message is logged in the diagnosis server logs: 

"Handshake failed (error:0909006C:PEM routines:get_name:no start line)"

This message indicates that the attempt to open a certificate file in the .PEM format failed. Most likely reason is that the file is stored with a different encoding, e.g. DER. 
Other reasons for the log message can be a corrupted file or a file that is not a certificate at all.

When a .PEM file is opened in a text editor, it should contain the human readable line "-----BEGIN CERTIFICATE-----"