I wrote a small script bound to a Google spreadsheet that reads an email-address from a cell in the last row and sends an email to it. The values are collected by a WebApp (not by Google form).
I tried all kind of triggers. The time driven triggers work, but the spreadsheet triggers don't work. I tried all of them. If I change manually some cell in the spreadsheet the onEdit trigger is working, but it doesn't fire up when the sheet was changed by another script.
Google's dev says : The onEdit() trigger runs automatically when a user changes the value of any cell in a spreadsheet. but it doesn't precise the change could be from script or not.
You'll find here a comment from HDCerberus :
I'm not at my PC to write a full response, but at a glance it could be the OnEdit trigger, which ONLY works when the sheet is edited manually, and NOT by a script. Are you expecting it to run when the sheet is edited manually or by a script?
Not every change triggers onEdit(). Please take a look on answer from topic Detect user inserting row or column in a google spreadsheet and reacting in a script - you will find registered bugs and one of them says that values written by scripts do not trigger onEdit().
onEdit()code in the web app, and run it from the web app. – Alan Wells