Review on Dell P2721Q Ultra Thin DisplayPort Certified 4K 3840x2160P Monitor with 🖥️ Flicker-Free Technology and Multi-Adjustment Stand, USB-C Connectivity - Dell 27 4K Monitor by Jared Simone

Bought this as a second iMac desktop monitor with Thunderbolt 2 output ports. Also bought a cable (active) to convert that output to HDMI, which this monitor accepts. The monitor just doesn't recognize it. I have used other monitors with an iMac and tested this monitor from a Dell laptop. Everything was fine, so it's definitely something with the monitor that doesn't work with the iMac. Other employees in our office received the same monitor and also had problems connecting the HDMI input to computers from other manufacturers. Contacted Dell Support but they were no help.