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.