Why SteamVR displays "Compositor is not available"?

(SteamVR - Compositor is not available)

If SteamVR displays "Compositor is not available"(pictured above), the reason may be one of the following:

• The USB 3.0 cable of the headset is not connected to your PC.
• HDMI cable of the headset is not connected directly with the HDMI port of the GPU which supports FOVE 0. (i.e it may be connected to a HDMI out on your PC's Motherboard).
• The FOVE Runtime is stopped (not running / not started)
• The FOVE Compositor is running

The FOVE Compositor must be stopped to use SteamVR with FOVE 0.

If FOVE Runtime is running and FOVE Compositor is stopped, Fove Config Tool displays it like so:

(FOVE Config Tool - FOVE Runtime is running and FOVE Compositor is stopped)

To stop the FOVE Compositor, you have to Disable FOVE Compositor Auto-start from right click menu of FOVE VR.
In order to disable the FOVE Compositor Auto-start, you have to Stop FOVE Runtime once.

(FOVE VR - FOVE Runtime is stopped)