U2520D, Asus N580G usb-c to usb-c connection (no signal)

@Psyhx  The display's user guide does say that the USB-C cable enables the USB ports on the display, but it doesn't say that it ONLY does that.  It wouldn't make sense for Dell to create a USB-C display and then include a data-only USB-C cable.  They'd either include a full functionality cable or no cable at all.  The more likely possibility is that your laptop doesn't support video output and charging through its USB-C port.  Both of those capabilities are optional on USB-C ports, and therefore not all systems with USB-C ports support those features.  But at the moment, the ASUS site appears to be having some issues, so I can't check that system's documentation.

Following this informations https://www.asus.com/support/FAQ/1042843/, my laptop should support Video by usb-c. The marking on the laptop suggests USB3.1 Gen1 Type-C + Display, with video display function, and theoretical bandwidth with a maximum transfer rate of up to 5Gb/s.

@Psyhx  One even more basic thing I forgot to ask.  Can you confirm you are plugging your system into the USB-C port on the underside of the display?  The USB-C port on the left edge of the display is a downstream port and is therefore meant to be used for USB-C peripherals that you might want to use with your PC.  It is NOT an upstream port and therefore you cannot connect an actual PC to that port to use that port as a video input.  Only the USB-C port on the underside of the display works that way.  Someone else here made this mistake recently.

@Psyhx  Ok, so your actual system has that DisplayPort logo shown in the image?  In that case yes video output should be possible.  But that does not mean that your system supports being charged over USB-C, in which case it would be normal that your system would not be charging from the display.  And just for clarity, the 5 Gbps limit means USB 3.1 Gen 1, but that doesn't affect video.  Video uses DisplayPort, which is not encapsulated as USB data.

But in terms of why video output isn't working, have you verified that your display is set to its USB-C input rather than something else?  Does Windows Display Settings recognize that another display is connected, even if it's not sending an image to it?  Did you try resetting the display to factory defaults before setting the display to its USB-C input?

If none of that works, do you have either another USB-C cable that supports video (not all USB-C cables do) to test with, just in case the cable happens to be bad?  Alternatively, do you have some other way to connect a display/TV to that system's USB-C output, such as a USB-C to DisplayPort/HDMI adapter?  Or another source system to test the display's USB-C input with?  Lastly, do USB peripherals you plug into the display work with your system when connected via USB-C?

@jphughan Thank you for your help. Two things I have discovered about my laptop: 

- It does not support USB-c charging 
- That USB-c port with that logo (D) means it export Displayport signal (if i use usb-c to DP cable it works correctly)

Thank you for your time, 
Greetings 

Yes, im using correct usb-c port. Also I checked is this problem occurs on Ubuntu system and yes it is 

@Psyhx  Ok, well if it doesn't support USB PD, then it would be normal for you to be unable to use the display to charge your system.  But you should still be able to send a video signal to the display using a regular USB-C to USB-C cable.  Did you see my follow-up post asking you about which USB-C port you're plugging into on the display?  You need to be connecting your laptop to the USB-C port on the underside of the display near the DisplayPort input, not the one on the bottom of the left edge.

@Psyhx  Do you have some other device that has a USB-C port capable of video output that you can test with the display?  If a USB-C to DP cable works, then a USB-C to USB-C cable should also work.  It's possible there's an issue with the USB-C input on your display, or it could be some strange interoperability issue with the specific combination of that system and that display, but without being able to test another source, it's difficult to determine.