U2717D, no connection with DP

Hello,

I am using the monitor U2717D for years with HDMI and it works fine. For some reason I now wanted to connect the PC with DisplayPort and it is not working! I have tried several cables (DP to MiniDP, 2x DP to HDMI) and none of them works. I have also tried several Laptops or desktop PCs and none of them works. This leads to the assumption that something has to be wrong with the monitor. I have read some articles about DP1.2 issues and tried to follow all advises. Unfortunately none of them worked. I am quite desperate now and want to ask you for an advise and whether there are fundamental issues with using DisplayPort on this device.

Waiting for your feedback,

Pat