VNC not working on Windows 10 Pro if Laptop monitor is off

UEFI (BIOS) Settings to Blame

Diagnosing the Problem

I bought a new Dell laptop with Windows 10 Pro. I already had several Dell laptops with Windows 10 (not Pro). I use VNC to connect to machines on my LAN. However, the new Dell laptop with Windows 10 Pro would not allow me to connect if the monitor had been shut off, either by a program or by the system to save power. I tried many, many things to solve this problem. One thing I tried was to have someone tap a key to which would turn the laptop monitor on. Then VNC could connect every time, but if the monitor was off and no one tapped a key then VNC would not connect.

Solution for me:

  1. Reboot and go into BIOS now called UEFI.
  2. Locate setting to allow Wake on LAN usually called WOL and turn it on.
  3. I also had to find a setting, do not allow sleep and activate that.

This solved the issue for me.

I hope this helps someone.