I have upgraded my test site to 4.4.1 and disabled file compression. I also looked at the clone of my test site (prior to the upgrade) and compared it to the upgraded site. If found that header.php and functions.php were different in the clone site. I copied them back from the upgraded site to the clone site and that fixed the original problem.

Now onto a new issue.

Enfold is interfering with the correct operation of Thrive Leads. On this page https://mp-prod.ghostpoint.com/partner-info/ when you click “Download Now” you get a popup to download the paper. It looks fine on the desktop. However, it does show correctly on a moble. If I disable Enfold and use another theme (I tested on twenty seventeen) if does work correctly and the pop-up resized itself for the mobile device.

I have a ticket open with Thrive as well

You have my permission to enable/disable/remove/edit anything you need to diagnose. I have a full backup of the site.