I'm sorry about the issue. What's the model of your Viewsonic monitor?
What's the issue with it?
Do you have windows 7 or 8 or 10, etc.?
Please reply at the box below. Thank you.
Very good. Right click anywhere on the desktop and select Personalize. When the next window opens, click on Lock screen. Scroll down to the bottom of that window and select Screen Timeout Settings. For your settings, you will want to choose the When plugged in options. Set them to what ever time you would like. Let me know if you need further assistance.
When you check the same settings, have you also checked to make sure your computer doesn't go into sleep mode? Let me know please.