NAVIGON was purchased by Garmin in 2011, and then shut them down in May 2018. They did not go bankrupt.
In May 2018, NAVIGON indicated that purchased apps should continue to work for at least 2 years. The latest map update for North America was a few months ago, and I believe this will be the last one. Their servers are still providing Traffic information as of May 25, 2020 (today), but I am unsure as to how much longer.