Clamshell with External Monitor doesn't work with DP to USB-c Cable

[caupljx]

I have an external monitor (Dell U2518D) connected to my 16' MBP, and have the 10.15.4 updated. When it's connected via a DP to USB-C cable, I can't seem to use it in clamshell mode. It connects fine when the lid is open, but when I close the lid, it just loses signal and the laptop just goes to sleep. And if I open the lid again, the signal still won't pick up until I replug the cable. Is anyone else experiencing this as well? Clamshell works well when connected via a HDMI to USB-C. I don't know if this is a monitor issue, cable issue, or the OS issue.

 

[Mojo1019]

Have you solved this issue?