To confirm:
You have changed this to your own folder ID ?
and this to your own script url:
Your google apps script web app is bound to the spreadsheet ?
The web app script is published as "you" (your google account)
with access for "anyone, even anonymous" ?
You have correctly re-published the web app after any changes ?
Is any data written to the google sheet ?
Here is a link for how to do it (you might want to try this as an example):