PitchWhite

Okay, im running an intermediary pc while i wait for my main rig be repaired. the intermediary is an: Acer Veriton X4620G Serial: 31001766 Bios version: P01-A3 my question is that im running 3 monitors that are running off a GTX 1070 but the 4th port isnt working for some reason, i imagine a faulty wire or solder job, regardless. I wanna use a 4th monitor but when i plug it into the onboard graphics, the monitor shows check cable connection. i know its not a cable issue because the monitor runs from a laptop with the same cable. any ideas would be appreciated

context: ive got a triple monitor setup consisting of 3 different displays, ive never had driver issues. i am using a radeon rx560 4g I decided to switch out one of my monitors to a different one and now, the following happens: 1. i turn my desktop on. 2. the new monitor *Only* displays the windows logo 3. the new monitor goes to sleep and the other 2 monitors function normally. I cannot find the new monitor in device manager, i have tried updating the driver via the AMD Radeon software and using safe mode to uninstall the driver and reinstall it. the Monitor serial is: 220BW8EB/75 any suggestions would be appreciated.