Checking for Chrome OS updates manually: 
• Turn on your Chromebook. 
 Connect your Chromebook to Wi-Fi.
 Sign in to an account.
 At the bottom right, select the time. 
 Select Settings. 
 At the bottom of the left panel, select About Chrome OS. 
 Select Check for updates.
 If your Chromebook finds a software update, it will start to download automatically, and it will ask you to restart after install.