How to reactivate Google Assistant after deactivating by changing Language? I had got Google Assistant for my Android device. However, I prefered Now On Tap for few features like the ones mentioned here and deactivated Assistant by changing the language settings as mentioned here. 

But I was wondering how do I reactivate the Google Assitant, I tried changing back the language to English(US) in Settings -> Google-> Search -> Search Language but to no avail.

How do I get back the assistant if I ever plan on using it?
Try clearing the cache for both Google app and Google play services in settings / applications. Also clear all your recent apps after doing so.