I don’t recall ever editing functions.php. My site has two wordpress themes installed:
On the domain “domain.com” I have a theme called AccessPress Lite. That domain and all of its subdirectories are all unaffected by me deactivating your plugin on the other theme (your plugin is not in the AccessPress Lite theme) used in a specific subdirectory:
The theme in the subdirectory “domain.com/subdirectory1” is GeneratePress. This is the one that breaks the non-amp pages when I deactivate the plugin. I get a strange message when I re-activate your plugin: “I’m Sorry, you are not allowed to access this page.” But If I try to do it again it works just fine.