Password protected pages problem

I’m trying to set up a plan room to host a few blueprints for contractors bidding on jobs for us. I’ve installed WP Download Monitor to do this. I’ve made a page and inserted the code to display the WP Download Monitor download page, which all works fine. However, I’ve set this page to be password protected and that is where I have a problem. The first time I visit the page I am prompted for a password. Once entered I can access the page fine. I can then close the browser and come back hours later and access the protected page without entering a password. I’ve disabled all plugins and switched back to the default theme with no luck. After some experimenting, I’ve discovered the only way to fix this is to clear the private data in my browser. So evidently the browser is remembering the password even though I told it not to. Firefox isn’t remembering it through the password manager so it much be caching a cookie instead. I would prefer a user be required to enter the password each time the page was visited or at least once the browser was closed. Any idea how to fix this?

You can view the site at https://www.morrispaint.com
I’ve set up a test page for this. Hover over the contact tab and a test room menu will appear.
The password is: password