Hey Miller! I hope you fixed your problem by now, but for the others who (like me) found this question because they are having the same issue here is how I just solved it:
There are two things you need to make sure are correct in order for it to work.
1) There are multiple spots on the back of the Dell monitor in which the mDP cord to display port fits. If you have it in the wrong one all you will see is the 'power saving' screen of death. The correct one is labeled 'DPin'. It looks like there are 2 of them, the one i'm using (which works) is the one directly to the right of HDMI 2.
2) After it is connected to the proper port, use the buttons on the front to select the input source as 'DP' which is the one on the top. I kept having issues because i assumed it was supposed to use 'mDP' (3rd from the top) but that wont work.
Hope this works for you as well! 😀