Sidebar not displaying for all

Greetings:

I have used Custom Sidebar for a site for several years. Typically, all works well. This time, however, things are going awry. There are some strange behaviors happening, as well.

The newly created page with sidebar is https://www.ahea.org/ahea-annual-conferences/ahea-annual-conference-2020/

When I review the page on Safari, Firefox, Chrome for OS and Firefox and Chrome for Android, I do not see the sidebar. I have worked on this site on 3+ different WiFi systems.

HOWEVER, a friend of mine in another part of the state (GA), using a PC, is able to see the sidebar that I want showing. He used Firefox and Chrome. He even sent me a screen capture displaying the sidebar on the page linked prior.

I have cleared cache on all my browsers, on the website server, and restarted my computer. I am still unable to see the sidebar.

What would you suggest to remedy the situation so the sidebar shows for all persons regardless of browser, OS, and location?

Thank you…fred

The page I need help with: [log in to see the link]