To anyone experiencing this issue, here is what we did to resolve it.
Thanks to some help from other community members, we analyzed the source code of the site and found that 20 links did not contain Https. We ended up updating those links manually; however, after making the adjusted changes, the certificate was still valid but not secure.
After much research online, we discovered this is a common issue when your website has been migrated. Also, this happens when you switch WordPress editors on your site.
Our site was developed with an editor called Elementor Pro.
Within Elementor Pro, there is a feature to update all of the underlying links that do not show in the page source code. (Ctrl + U) There were an additional 127 links not found when viewing the site code.
For anyone with Elementor Pro, the location to update the behind the scene links is here:
Elementor > Tools > Replace URL.
Enter both the old URL and the new URL, then click Replace and you are good to go!
Thanks again to everyone who responded and or messaged!