Failed to side load sample app

[mithrandir]

Followed the whole instruction, failed at uploading app manifest.

It said, something went wrong, visit aka.ms/teamsdocs for details. Even that URL redirected to not-existing page error!

There is not error message or error code, I have no idea what went wrong.

[asnow003]

That button I think says copy error details to clipboard. Once you do that can you paste what the response is here. Also, could you go to App Studio and go to the "Validation" tab and run your zip file through the tests and see if that gives you some more hints on what is wrong... You can find it in App Studio or this link: https://aka.ms/teamsappvalidation

[asnow003]

Also, would you be able to provide your zip package to us if the validation doesn't give you any helpful errors.

[SlyCaptainFlint]

I'm seeing similar behavior. The validation flagged a bunch of errors related to the icons (the size of the color icon is wrong, and the colors/size of the outline icon are wrong, too), as well as warnings related to the short description repeating the long description, and tunneling URLs.
I fixed the icon issues and the warning about the description, but I need to use tunneling URLs while developing, and I can't imagine that's the issue, since I'm just trying to sideload the app. There is absolutely no useful information in Teams when the sideload fails - this is what I see

Attaching my manifest. I tried the upload with very minimal manifest modifications (just updating the app id and URLs where required) and got the same result, so I tried to pare it down to just the capabilities I needed, but no luck - same error
manifest.zip
.