Service Unavailable

All I am getting when I run my new Web app is:

Service Unavailable
HTTP Error 503. The service is unavailable.

Note: all the demos work, it is just when I try to make my own app from scratch.  My guess is that it can't find the folder with all translated code.

In debug all I see is index.html, no other files.  Contents:
<HTML><HEAD><TITLE>Service Unavailable</TITLE>
<META HTTP-EQUIV="Content-Type" Content="text/html; charset=us-ascii"></HEAD>
<BODY><h2>Service Unavailable</h2>
<hr><p>HTTP Error 503. The service is unavailable.</p>

This looks COMPLETELY not like what is in the generated files.  What am I missing?

UPDATE: This is occurring when compiled with Delphi 10.2.3, when I try exactly the same project using Delphi 10.1.1 it works fine.

What I can't explain is how running all the demos from Delphi 10.2.3 still works.

Did you compare the URL with which demos are started versus your app?

Yes, the URL is what is expected.

Could you please provide more details? What is the URL of one demo that works? What is the URL of your app that doesn't work? 

Also, could you please check TMS Web Server (you have an icon for it in Windows tray that you can double click) and see what servers are running there, serving files from which folders? I suppose you have server for demo URL there but not for your app?