Google Sheet Script Error: "Sorry, unable to open the file at this time."

Question

I created two scripts for a small business which do the following:

Script 1: Creates a new blank invoice which is a copy of an invoice template

Script 2: Converts the invoice into a PDF file and emails it to the person in charge of working with invoices.

How does it work?

There are two default sheets:

Sheet 1: "Invoice Template" (Hidden) with a button linked to script 2 (The script converts the active sheet to pdf)

Sheet 2: "Menu" It's basically just a button that says "Create Invoice" which then runs script 1. Invoices are named as "Invoice " + sheet index - 2 so the first invoice created would be Invoice 1, next Invoice 2 and so forth.

When I link the buttons and run everything on my own spreadsheet it works perfectly however when I move the script to a workbook owned by someone else it only works for me and not them.

• When they click on any button associated with a script, it breaks the link between the button and the link.
• When they click on tools -> Script Editor they get the error: "Sorry, unable to open the file at this time."

When I run the script for the first time inside of their workbook this message appears, "This app isn't verified" where I then have to click a few buttons to let it run, however, when I run it in my own work Book, Google just asks if I want to give the app permission.

Basically, I am just trying to make sense of this and figure out what I need to do so that other users in the workbook that I don't own can run the script. Anyone have any experience with something like this?