18xx Dream Spreadsheet Authorization Issue
Google has created a strict authorization requirement for Google Apps Scripts running on Google sheets. The script author can partially circumvent this by including @OnlyCurrentDoc in a comment at the start of the script.
Because of this, these Dream Spreadsheets are considered by Google to contain unverified apps and you must navigate an authorization process the first time that you press the New Tab button on a newly copied sheet.
The following is a three step guide to this process:
The first time that the New Tab button is pressed the pop up box shown to the right will be displayed.
Simply press the continue button to proceed.
The Choose an Account box will be displayed next.
Your Google account should appear there.
Click on your account to continue.
This box is Google's last attempt to scare you off. Don't let it.
Just click on Allow in the lower right corner.
That's it. You now have access to the New Tab script and you will not have to bother with this process again on this spreadsheet.