office addins - Sideload failing for web outlook add-in per official guide

Question

Been developing a small add-in that was working fine... now I can't seem to get any local add-in project sideloaded from localhost as the MS guide describes! (https://docs.microsoft.com/en-us/office/dev/add-ins/quickstarts/outlook-quickstart?tabs=yeomangenerator)

Tried npm start(instead of npm run dev-server), output as follows:

The dev server is running on port 3000. Process id: 16396
Sideloading the Office Add-in...
Error: Unable to start debugging.
office-addin-debugging: Unable to sideload the Office Add-in.
Error: Sideload is not supported.

The projects used to show up in the ellipsis menu on web outlook, now they won't load at all.

Tried creating a brand new project, no luck.

checked this very similar thread, no luck. Unable to sideload the Office Add-in when running 'npm start'

...oof

Answer 1

Installing your test Manifest I see the following:

In the Add-ins button:

In The ellipsis I see:

So it's working for me in OWA, and I also saw similar results in Win32 Desktop Outlook. Are you on a private exchange server? Does your manifest work on an Outlook.com account?