P2417H vga port "no input"

We need more data.
* To what computer model is the monitor attached?
* What video card/GPU is in the computer?
* What video out ports are on the video card/GPU or computer?
* List all monitor cables and adapters attached to the computer and the ports they are using and how they are connecting to the monitor. Example =
Computer video card GTX 1080 DVI out port --> DVI to VGA cable --> P2417H VGA in port

Dell Precision T5610

Nvidia Quadro K600 DP -> DP converter to DVI cable -> IOGear GCS1642 -> DVI to VGA cable -> P2417H VGA port

Nvidia Quadro K600 DVI -> DVI cable -> IOGear GCS1642 -> DVI to DP converter -> P2417H DP port or

Nvidia Quadro K600 DVI -> DVI cable -> IOGear GCS1642 -> DVI to VGA cable -> P2417H VGA port

Nvidia control panel will respond to P2417H monitor when connected and disconnected.  Monitor shows "No Input" on either port.

Second machine with same problem

Dell Precision T5500

Nvidia Quadro FX 580

Was -- FX 580 DP->DP / VGA converter -> VGA cable -> Dell 19' monitor VGA port -working fine

Then FX 580 DP -> DP / VGA converter -> VGA cable -> P2417H VGA port  Monitor shows "No Input" on VGA

Had to use DP cable to P2417H DP port.  Why won't the converter work on the P2417H but will work on the 1907FPV1?

All of those adapters, cables, dock, are just confusing the issue.

Nvidia Quadro K600 DP out port --> DP to DP cable --> P2417H DP in port
Nvidia Quadro K600 DVI out port --> DVI to VGA cable --> P2417H VGA in port

Nvidia Quadro FX580 DP out port --> DP to DP cable --> P2417H DP in port
Nvidia Quadro FX580 DVI out port --> DVI to VGA cable --> P2417H VGA in port