I am in the process of restoring a CRT monitor as it was left in my shed for a long time and some rust is around the VGA male cable end of the monitor and VGA cables have 15 pins but I noticed mine is missing a pin then I looked at another monitor and it too is missing a pin but in a different location, why is a pin missing from the monitor cables I looked at VGA wiki but it does not mention this.
Not sure which Wiki you're talking about, but https://en.wikipedia.org/wiki/VGA_connector is clear:
Pin 9 KEY/PWR formerly key, now +5V DC, powers EDID EEPROM chip on some monitors
It's a key pin, i.e. one intentionally left empty to ensure correct orientation of connector.
In very late VGA systems it was co-opted for +5VDC for EDID, to allow the monitor to talk back to the card with its capabilities, but with old stuff that's not going to work and you encounter VGA connectors with the key intentionally blocked - so that's why you don't want the pin in the cable either (unless you support EDID).
