Most probably nxsteam error's usually occurs on Riders of Icarus type of games.
So, in order to fix this issue, try this:
- Turn off UAC Notifications.
- Run Steam as an Admin Privileges
- Hope it fixes.
1. Please ensure that you meet the minimum specifications to run Riders of Icarus >>http://icarus.nexon.net/en/news/article/14184/riders-of-icarus-final-system-requirements
If you do not meet any part of the minimum requirements, you will need to upgrade your machine.
2. Please ensure your Windows OS and video card drivers are fully up to date, and current. This can be accomplished by running Windows Update, and searching for drivers on your video card manufacturer's website.
3. Please try disabling (or allowing Riders of Icarus as an exception) any anti-virus programs (AVG, Avast, Kaspersky, etc.), personal firewall software, or potentially even Windows Defender when attempting to launch the game. We've found that oftentimes an anti-virus program is being overzealous and blocking your connection to the authorization servers.
4. Please attempt to "Verify" your steam installation. Right click on the game in your Library >> Properties >> Local Files Tab >> Click "Verify Integrity..."