This question already has an answer here:

I recently install ubuntu 18.4 and i tried to install Gnome Shell Extension in Firefox, the extension has been install, but show this 'Although GNOME Shell integration extension is running, native host connector is not detected. Refer documentation for instructions about installing connector.'. I try to install same extension in chrome and show the same error, and in Chromium the same error i install Ubuntu in 2 PCs and the error to persist

marked as duplicate by muru, karel, pomsky, Fabby, Thomas Sep 7 '18 at 9:36

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.