Load on task bar, won't open

Same issue here. Please help.

Are you on windows 10 that was recently updated?
If yes check or upload output_log.txt

If it contains this error:

IndexOutOfRangeException: Array index is out of range.
  at UnityEngine.Display.RecreateDisplayList (System.IntPtr[] nativeDisplay) [0x00000] in <filename unknown>:0

try starting the game while holding shift and check if in opened dialog you can select Monitor or if that list is empty.

If monitor (display) list is empty there might be some problem with scaling setting after windows 10 update.
Win10 is doing something with display scaling feature so it can run on all kinds of different display resolutions...

If you are using DVI, HDMI or DisplayPort connection to monitor you might try to use GPU scaling instead of Display scaling.

Perform scaling on: GPU
Or "No scaling" mode instead of "Aspect ratio".

Right click on desktop and select "Nvidia control panel" or "AMD Radeon Settings"
on nvidia cards it is under "Adjust desktop size and position"

https://forums.kleientertainment.com/topic/85690-windowes-update-and-now-issues/
https://forums.kleientertainment.com/klei-bug-tracker/oni/black-screen-of-death-on-w10-1709-r8127/
https://steamcommunity.com/discussions/forum/1/1480982971174752598/

This problem is not specific to ONI and you can find some more info also in other games forums.