Makvision M2929D4-TS SVGA will not accept signal from AMD, works with Nvidia

[Noob_Rectifier]

I'm trying to get emudriver working with this monitor and I can't get it working for the life of me.
The cab that I bought was functional, but was in need for an upgrade. I've tried an hd 6950, two r7's and an r9 380. I'm fairly certain I've set them up correctly, going as far as running TeamViewer and only having the VGA plugged in. I never get a picture when going through OSD.
 
However, this monitor instantly sees a Nvidia 9400gt as well as my old Thinkpad t420.
 
I'm totally lost. I know these makvision monitors can be finicky but to have nothing from AMD and functional with Nvidia is odd.
 
I have also used CRU to set the display to 800x600 at 56khz. If I remember correctly, I at least got a black screen instead of the dreaded "disconnected" message.
 
What can/should I be doing differently? Any help is definitely appreciated