U3223QE, Mac no longer detects it, goes black screen

Dell Support must verify the ownership and warranty status. Click the blue "Get Help Now" on the right to start a private live chat session. Share the private U3223QE Service Tag with them.

Try the initial troubleshooting.

* Turn the Mac off
* Turn the U3223QE off

* Disconnect EVERY cable (including power cable) and USB/UBS-C peripheral from the U3223QE
* Press and hold in the rear U3223QE power button for 8 seconds

* Connect only the power cable and the 1 M USB-C to USB-C cable to the U3223QE
* Connect the other end of the 1 M USB-C to USB-C cable to the Mac

* Turn the U3223QE on
* Turn the Mac on

What happens?

@DELL-Chris M​ I tried already all this steps and monitor is not working. Also, I tried connect my old dell monitor with same cable USB-C and it's working. Also, I tried do connect another Mac to this "not working" monitor and also, screen black and nothing happens. 

Live Chat Session, for me is not available, it says 

From who did you purchase this U3223QE?

In what country?

@DELL-Chris M​

I live in Croatia, and I bought it from reseller Senetic, https://www.senetic.hr/product/DELL-U3223QE

But I can see that country is named to Lithuania in data on Dells web

The Senetic site states that you need to go through the Dell site here for Support of a product purchased from them.

@DELL-Chris M​ Yes, that is what I did. This customer support with DELL is really wild.