Sudden problems with Youtube Data API authentication and quota error

Question

Last year I was building an application to create my own YT dashboard. It was based only the code of a tutorial They basically authenticate a user via OAuth and send requests to get channel data or playlists of the authenticated user.

I was trying out both the original tutorial app and my own (after a few dormant months) and they suddenly don't work anymore. Meaning: I can authenticate on both, but on the original version I get a 403 error telling me: "The request is missing a valid API key." (on requesting channel data)

This is confusing because the API key is never used because only the OAuth client id was necessary.

And on my own fancy version, I get a 403 error telling me that I've exceeded my getting started quota. (on requesting the users playlists)

Looking at my quota page:

I can see, that queries per day (why is it there twice?) is somehow set to 0.

Perhaps creating a new OAuth 2.0 Client ID or a new API key would solve these errors, as was suggested in another post.

But since I'm planning to use the YT Data API in a real project soon and want to prevent this from ever happening I would like to understand what was going on. Why the daily quota limit is suddenly turned to 0 and how to go about it when that happens. Or at least how to contact google about it.

Perhaps some of you have some insights.

UPDATE: I've just found this post reporting, that after 90 inactive days, the quota is automatically set to 0. Now I created a new OAuth Client Id and replaced the constant in my code. Nothing changed so far. Perhaps I have to wait 24h. Or perhaps I have to fill out this form which apparently can lead to months of back and forth email nonsense. I sure hope not.

Answer 1

It seemed the only viable option was to create a new project with new credentials. (And one should not forget that the YT Data API has to be enabled again for the new project.)