If you check out the Google News Help forums you will see many many complaints from news publishers that their news site is no longer in the Google News index. Supposedly hundreds of publishers who were listed in the Google News database are no longer qualified to be included in the index anymore.
Some are getting notices of the removal while most say they did not get the notice. I guess the quickest method to see if your news source is still included is to go to the Google News Publisher center and check the status:
Or you can try to a site command or searching for a title of a recent story you just published.
Here are some of the threads in the Google News forums:
Those that did get notices may have received a response from Google that says they "periodically review news sources" and when they reviewed this specific news source they have they "can no longer include it in Google News." Here is a screen shot of such a notice:
I am not sure how widespread this is, if it is a bug, if this is a fake news clean up attempt or not. Google has not officially responded in the Google threads yet.
Forum discussion at Google News Help.