I've seen other posts on the internet and unfortunately I'm having the same issue. When my computer goes to sleep then wakes up, I generally have to turn my monitor off and on again to get it to work. About half the time I even have to do it two or more times before it starts working.
Very frustrating. It's such a gorgeous monitor too. Some stats about my computer:
-Video card: XFX R7 260X
-Running Windows 8.1
-Using the DisplayPort cable that came with the monitor. The mini side is connected to the monitor.
-My UP2414Q is my sole monitor
-Does it with DisplayPort 1.2 mode on or off
-My old 24" monitor ran fine with no problems on this computer, seems unique to this monitor
-I installed the monitor driver for this monitor from the Dell website
I would really appreciate some help here.