Getting usage limit error from server - youtube-api

Question

On Friday (6/24/2016) our youtube app crashed giving us the following error.
{
"error": {
"errors": [
{
"domain": "usageLimits",
"reason": "dailyLimitExceededUnreg",
"message": "Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.",
"extendedHelp": "https://code.google.com/apis/console"
}
],
"code": 403,
"message": "Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup."
}
}
The code that was run was a simple API request to check the state of a video. It has also been running without any problems for over a year.
curl https://www.googleapis.com/youtube/v3/videos?part=contentDetails,status,snippet&key=XXX&id=XXX&maxResults=50
A few thoughts:
This message makes no sense since we are passing our key as a parameter which does authenticate us. I understand this can mean I need to use OAuth but this would be a change since this has been running without errors for over a year.
When I checked our API console I found that the youtube api was marked as disabled (this changed as we enabled it to get a key last year) and I do not see any usage limit errors when I check usage in the console.
I have also found making the request to the API from a browser on my desktop works but using curl on our server gives the usage error. This indicates there is some issue with our server.
Can someone help me understand what's going on? Are there IP blocks for the API? Did Google make a change recently that would have reset my console and caused an error suddenly in our code?
Any thoughts would be greatly appreciated.

Answer 1

"Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup."
I've come across this error before. It's not that complicated. 2 things I can suggest:
You're access token has expired. You need to generate a new one. Read Implementing OAuth 2.0 Authorization.
Register a new API key in you're GDC.
Also, try oAuth Playground for testing.