David Kimura PRO said over 3 years ago on Autocomplete with StimulusJS :
  can you post relevant code? Also, check your browser's console for any errors as that could prevent controllers from firing. In the initialize() function, you could put a console.log within there to make sure that it is getting triggered. If it isn't, there could be a naming issue or something else. Also, when you register the autocomplete library (likely in the index.js in the controllers folder), make sure you're using that name as the data-controller.