P2419HC, Lenovo P1 ThinkPad, does not work with USB Type-C?

@emph07  Are you using a USB Type-C cable specifically rated for DisplayPort Alt Mode?  Some USB Type-C cables only carry power and USB 2.0 data, not video or USB 3.x.  On that subject, is the P1 even detecting a power source when connected to that display?  With that system you'd still want to keep the system's own proprietary power source plugged in since the P1 is designed for 135W, which is more than the display provides, so if you run the system from the display then you'll likely encounter slow battery charging and reduced performance.  But it would still be useful to know whether the P1 is interfacing with the display at all, even as a power source.  And have you tried both of the TB3/USB Type-C ports on the system?  Either should work, but may as well test both.

I have used the original USB Type-C cable provided with the P2419HC. I use the lenovo 135W power supply. I've tried both USB Type-C ports. As soon as I connect the P2419HC to the pc I get the message. The monitor works fine with HDMI. I read through this.

@emph07  Very strange. The ThinkPad P1 definitely supports DisplayPort Alt Mode and Power Delivery over USB-C, so it should work if you’re using the cable that came with the display. At this point the only thing I can suggest is to isolate variables to identify the culprit, meaning try another USB-C cable if you have one rated for DisplayPort Alt Mode, or try another USB-C display, or try another USB-C laptop as a source if you’ve got one. And I guess use Lenovo Vantage to check for any driver or firmware updates in case this is some weird glitch that might have been fixed with an update.

Hi. Another cable did not help. I assume it's a problem on Lenovo side, rather software.
I hope that Software Update will help. Maybe I shoud ask the Lenovo Support?
Another solution would be to use a docking station but it is an additional cost.
Thanks for help anyway.

What is also strange, I've managed to update the Firmware in this monitor using HDMI and USB-C.

I get the message, in german, which means that "display connection may be restricted"

@emph07  Very strange indeed.  I admit I'm not sure what to suggest at this stage.  I personally have an X1 Extreme Gen 2, which is quite similar to the P1 Gen 2, which is itself quite similar to the original P1, and I'm able to use USB-C displays just fine.  I suppose a hardware issue other than the cable is a possibility.  But I'm also guessing that if you had another laptop to test the display with or another USB-C to test the laptop with, you'd have done that already.  A docking station might change the equation if this is just a bizarre interoperability issue that affects the specific combination of this system model and display, but as you say that would be extra cost, and if it's NOT an interoperability issue like that, it might not even solve the problem.

@emph07  Great news, although that’s rather strange since the P2419HC is a regular USB-C device, not a Thunderbolt device, so I wouldn’t have expected Thunderbolt drivers to make a difference. But at least it works!