Now here’s what happened to me last night. Follow me closely, as this will explain why you might get a very specific error message upon activating the plugin on staging or production environment one day, that would imply you have a nulled unlicensed plugin.
I installed my original licensed WP Rocket on my local development environment. As it was an older package, I decided to update it first, and then push it to staging. And so I did.
Once I pulled the latest code from my repo on staging and activated WP Rocket, I tried to configure the plugin, but got this message instead:
License validation failed. You may be using a nulled version of the plugin.
A tiny detail I need to mention here – the staging environment is not reachable publicly, as I’ve protected it behind a basic authentication wall.
So, it turns out that if you install WP Rocket in one place and then move it to another, protected WordPress instance, the plugin will not be able to work, as it will assume that the user is trying to configure a compromised plugin with malicious code inside.
How did I fix this?
I removed the new version of the plugin, then installed the original one, without activating or updating it on my local environment. Activated it staging and it worked just fine there.