If your DVI - VGA adapter is passive you may need to use a ACTIVE DVI-VGA Adapter for the computer to see your VGA Monitor.
If your Motherboard or GPU card outputs DVI-D then you must use an ACTIVE DVI-D - VGA Adapter otherwise it won't work as per this Tom's Hardware Forum: DVI-D to VGA adapter won't work - [Solved] - Displays
BEST ANSWERAug 10, 2017, 1:46 PM
Modern GPUs do not have analog VGA output on their DVI connector and won't work with passive DVI-to-VGA adapters. You need an active adapter which has analog-to-digital converters inside.