Helmut said almost 4 years ago on Autocomplete with StimulusJS :
Hi David, thanks for the quick reply! I will triple-check things tomorrow and post code, but can say that I see no errors in the Terminal log, and I put a "PUTS "THE INDEX IS BEING CALLED!!!" message into my Client controller Index action, and it never appears (in my bigger project, I have Invoices that belong to Clients, instead of Books that belong to Authors).

But one question: you say "In the initialize() function, you could put a console.log within there to make sure that it is getting triggered". But where would I find the actual controllers that Stimulus-Autocomplete installs? There are no autocomplete controllers in my Javascript>Controllers folder (where all my other stimulus controllers are), and I figured that the Autocomplete controllers were not accessible because I installed them via Yarn. I know Stimulus is generally working in my app because lots of other parts of the app use it (including your Nested_Forms controller, which has been great!). 

Thanks!