Customer told connection is not private

I have a customer support mailing system where members of my membership site are sent weekly emails with links to pages on my membership site (which is on a secure server).

One of my members has told me she gets a message when she clicks one of the links which says:

========================
Your connection isn’t private
Attackers might be trying to steal your information from
jw122.infusion-links.com (for example, passwords, messages or credit
cards).
NET::ERR_CERT_AUTHORITY_INVALID
This server couldn’t prove that it’s jw122.infusion-links.com; its
security certificate is not trusted by your computer’s operating system.
This may be caused by a misconfiguration or an attacker intercepting
your connection.

Continue to jw122.infusion-links.com (unsafe)

What is that all about? Why are my customers being told that my service is unsafe! Not happy about this.
What can I do about it (if anything).

Thanks

I get the same error when I click that link. That link isn’t secured and doesn’t have an SSL certificate attached to it. You need to have the SSL in order to secure it.

To recreate the error the customer is clicking click this https://www.jw122.infusion-links.com/