Rocket Loader is a feature by Cloudflare that can help with page load time. Unfortunately, the method in which it does this is very aggressive, is a beta product, and can often break JavaScript (including Mediavine ads).
Mediavine Publishers need to disable Rocket Loader immediately.
There isn't a super easy way to tell if you are running this or not, so our first suggestion would be to contact your host or Cloudflare support and ask them if Rocket Loader is activated, then ask them to disable this feature if it is.
If you are technically inclined, you can pull up your site's view source code and search by using Command + F or CTRL + F for "rocket-loader" to see if it's currently running on your site.
If that is in your code, you are running Rocket Loader, and this applies to you.
You can still run basic Cloudflare without enabling Rocket Loader. To disable Rocket Loader, open up your Cloudflare dashboard and go to the Speed tab. Scroll down to "Rocket Loader," and toggle the feature off.
If you've enabled those settings and still would like some help to improve pagespeed, it might be best to work with a developer to find some other solutions. Things we recommend include:
Removing as many external JavaScript scripts as possible.
Compressing images using one of the many plugins out there.
This isn't something that we can directly troubleshoot or assist with here at the Mediavine help desk. We recommend contacting your tech help for direct support.