Purchased two of the U2717D monitors and set them up with a Dell E6440 and an E-Port Plus Advanced docking station. Monitors worked fantastic initially using the two DP to mDP cables provided with the monitor. However, any restart, sleep mode, power off/on resulted in at least one of the monitors having a black screen "no signal" message. Although the computer recognized the monitor as being connected. Frustrating part about this problem is that it was tough to replicate; sometimes the problem would be one monitor or the other; sometimes just unplugging and plugging in the mDP cable would fix it. 

Read nearly every post on these issues and what worked for me was disabling the DDC/CI setting in the monitor menu under Other.

Now my monitors come up perfectly after sleep mode or restarting. Wanted to add this to the forums as a potential solution for others although I would like to know what might be causing this? Would be nice to be able to use that DDC/CI feature along with the DDM software at some point.

I had tried the fixes below before trying the above option:

- New cables

- Turn off monitor sleep setting

- Update BIOS, graphics card driver