“SpreadsheetApp.getUi() cannot be called from this context”

Question

In a Google Sheets spreadsheet, I want to show a modal dialog created from HTML, then run a function, then close that HTML prompt automatically.

The dialog should st

Answer 1

Ui Dialogs can not be called by time triggered functions, they have to be triggered by a user action, that's to say a click on a menu item or some sort of button that calls the function showing the UI.