Why has youtube-v3-api stopped working?

We've been using youtube-v3-api for quite some time now, but all of a sudden it started responding to a 403 error saying that access should be enabled.

Here is the error message:

{
  "code": 403,
  "errors": [
    {
      "domain": "usageLimits",
      "message": "Access Not Configured. YouTube Data API has not been used in project {projectId} before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/youtube.googleapis.com/overview?project={projectId} then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry.",
      "reason": "accessNotConfigured",
      "extendedHelp": "https://console.developers.google.com/apis/api/youtube.googleapis.com/overview?project={projectId}"
    }
  ],
  "message": "Access Not Configured. YouTube Data API has not been used in project {projectId} before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/youtube.googleapis.com/overview?project={projectId} then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry."
}

      

        
        
        
      

    

But the api is included and it worked for months:

We are using api with oauth2 tokens and API keys, but we get the same error for both.

What could be the problem?

I tried to disable and reuse the API, but it didn't help.

Update

Google support suggested that the problem might be caused by the daily quota limit set to 0. However, we cannot edit this quota as shown in the picture, although we have full administrator rights to do so.

Has anyone experienced this? How can we increase the quota? We have already filled out the quota limit extension form and are awaiting a response, but I think we should be able to set the quota to a healthy level in the developer console.