Is it really possible to make chrome extension work?

[EagleEthenFossey]

I just tried many times to let chrome extension work. But i just can't get what i want.
I uploaded the extension zip to web store and published it to testers.
From webstore, i found the app with url and let it installed to my chrome.
But totally nothing happens.
I think if the extension app is perfect, some kind of options might be working for it or at least try to confirm gmail api.
But unfortunately no.
Even in my gmail and dashboard.
Hope nothing is wrong with the code.
Can anyone explain the exact step and code?
It might be better to send video.
Thanks.

[dystonic]

Hi, upvote - I've been working on this for two days now, are there any updated instructions you can share?

[paddycarver]

So I believe the root cause of this is that you need to make sure you have the GMail permissions not only in your Chrome extension manifest, but you also need to select them when creating the OAuth2 client, as per this part of the instructions, you need to make sure on the OAuth consent screen page, you add the scopes https://www.googleapis.com/auth/gmail.send and https://www.googleapis.com/auth/gmail.modify to the "Scopes for Google APIs" section, or you'll get an error trying to ask for those scopes when instantiating the JavaScript client.