Connecting display to Late-2014 iMac 5k or Mid-2012 MacBook Pro

Hello,

I’m trying to connect a second display to my iMac and/or MacBook Pro while working from home during this pandemic and neither seem to recognize the display. My MacBook flickers when I plug in the cable to the mini display port, but that’s it. In Settings > Display, the Arrangement tab doesn’t even show up...

The monitor is a Achieva Shimian 27" LED Monitor S-IPS, 2560 x 1440.

I've tried two different adapters and also tried a Dvi to mini display port cable.