How Do You Troubleshoot the OpenVPN Issue “insufficient key material or header text not found in file”?

Problem scenario
You get an error message when you run openvpn. You are trying to start the client service. You get "insufficient key material or header text not found in file". What should you do?

Possible Solution #1
Backup your client.conf file.

Find your tls-crypt.key file. If you have none, run this:

openvpn --genkey --secret /etc/openvpn/tls-crypt.key

Copy every line in the tls-crypt.key file and paste it into a particular location of the client.conf file. The client.conf file should have a tag. The content should go on the line below. This way what you paste will end above the tag.

This answer is a presentation that was adapted from this website.

Possible Solution #2
Reinstall OpenVPN on the server and on the client. Completely start over.