The site is here https://mf.rps.ltd/ as you can see from the attached the client is getting a warning pop up on their pc when trying to view the site, how can this be stopped please?
I can see in the popup it has mentioned revolution5.themepunch.com but i don’t find any reference of it in your site source code.
I can’t reproduce the issue by visiting your site orelse i would have troubleshooted it.
Please clear WP-Super-Cache or temporary disable it that you are using on your site and then troubleshoot why only your client is facing this issue. Whether it is his browser version or location specific or anything else.