Member of my site getting a 403 page

To Whom it May Concern,

Greetings. I run a membership site. One such member has been unable to access my site, as every time she tries to access it she gets a message saying that my site is not secure. I have never encountered this before. Do you have any idea what could be causing this?

She is using a PC, running windows 10. The web browser she was using was google chrome. She has no problems with accessing the site from her iphone or ipad. I have also attached an image of the error code (is that the right term?) she sees when she opens her security program. I think the security program she is using is called eset security.

Any light you could shed on this would be much appreciated. I look forward to hearing back from you.

Best, Ferris