well, that’s strange. I was just running a test, and added with a Header plugin this code.
When the plugin is active, I can see the google test result as okay.
If I de-activate the plugin (and therefore the code is removed from the header) I get the warning message from google, that my site is not mobile-friendly.
That means… somehow.. that line of code doesn’t seem to be read just by using the theme on its own?
I deactivated also other plugins, just to make sure.. that’s the source.