WordPress 5.5.1 Fortuna 3.00 Issues

Hello, we had several issues occur recently when we updated plugins and WordPress. You can see a test version we’re trying to fix here: https://millsins.com

The entire header area is supposed to have a Revolution Slider in it and it is not loading and further down the page the testimonials section disappeared as well as a background image…

This is an older theme, so not sure if finally past its prime or not. Any help or ideas would be appreciated. I may try to revert back to an old version of WordPress in order to see if this fixes the problem in the meantime.