This page is not being served over http — the app cannot reach Google. A browser only lets a page call another website when the page itself came from a web address. Opened straight from a folder, every request to your Apps Script is blocked before it leaves your machine. Nothing is wrong with the backend.

Any one of these fixes it:
· put this file wherever the Sales CRM is hosted and open it from there
· drag it onto app.netlify.com/drop — free, takes a few seconds
· in its folder, run python -m http.server 8000 and open http://localhost:8000