Problems with DELL P2415Q monitor not waking from sleep.

Wish I could say that worked for me unfortunately I have to leave a Thunderbolt cable plugged in and an HDMI cable in the monitor. When the HDMI refuses to wake the monitor I have to select the Thunderbolt input and vice versa.

Similar issues here. Monitor worked fine under Yosemite (I was slow to upgrade my Mac Mini) and never had this issue. After I went to Sierra in December, it started occurring. Now it's almost daily. I've tried every workaround posted except for replacing the cable (one's on the way) and no joy and I have to restart the Mac to fix.

This would seem to be a Mac issue as I've tried disconnecting the cable from the Mini and switching it to my MBP. The monitor immediately woke up and worked fine, but when I switched back to the Mini, it wouldn't respond. I suspect there's a driver issue that (pardon the layman's terms) the Mac think's it in one state and won't send another "wake up" signal to the monitor, or there are multiple levels of signaling and it's not sending the right one. Or possibly there's some HDCP protocol problem or key exchange that isn't taking place in certain scenarios.

Either way, the monitor clearly works, with that specific cable, and the only difference is which Mac it's hooked to.

I have one Dell P2415Q monitors in my nMP and sometimes that monitor does not wake while my HP monitor wakes. I just press Power button on the monitor to turn it off and then when I turn the monitor back on it works.

I just live with it.

Are both of your monitors connected to a different Thunderbolt buss? There are three TB busses

Hi, just wanted to add that this problem is still around for those of us with these Dell monitors. I have 2 P2414Qs and they both have the same issue. Works perfectly while on, but don't wake from sleep reliably.

The only difference for me is that using the power buttons on the monitor always works eventually. My procedure is to turn off the monitor (press once), wait a couple of seconds and then turn on again (press once).

The delay seems to be required (in my case) for the Mac Pro to notice that the monitor has disappeared.

Also, a tip that makes this easier to live with is to turn on "Monitors as separate spaces" in System prefs. That way, the Mac Pro seems to remember which window was on which monitor, rather than dumping them all onto the left most monitor.

I have the same problem with this monitor and my MacBook. The only way I'm able to get it back is to turn the power off to it completely (on the power strip) and turn it back on. The power button on the monitor itself doesn't respond at all when it gets into this "situation."

I have the P2415Q connected via the mini-display port (Thunderbolt port). My display wakes up after the screen goes to sleep without any issues.

My input source on the monitor is DP (not miniDP). So the cable is miniDP to DP (small to large).

MST is off. I have not noticed and difference with MST on (multi-stream)

Resolution is running at 3840x2160 at 60Hz.

My system is MacBook Pro 2015 15 inch El Capitan 10.11 with Graphics Radeon R9 M370X.

I am only running one external monitor and the built in display.

I hope this helps.

By the way, I love this monitor. It is a larger version of the built in retina display. The fonts are very smooth and makes working on the Mac a pleasure and I feel it has reduced my eye strain. Much better than my old 1920x1080 monitor.

M Sargent wrote:

MST is off. I have not noticed and difference with MST on (multi-stream)

Resolution is running at 3840x2160 at 60Hz.

Unfortunately, the 2414q requires MST (DP 1.2) to achieve 60Hz. At least mine does.

Funny thing: I have the exact same configuration and it's nothing but trouble. Not only will the Dell not recognize the Macbook (15" Pro 2015) when it wakes up but the Macbook itself will hang with no or distroted graphics and has to be hard-reset. This happens approx. 10 times a week during usual office use.

Very annoying thing.

But thanks for pointing out that there are systems that do work. I will try a different cable.

I have same issue, sometimes my 2 x P2415Q monitors wont wake up --- only thing which works is to disconnect monitor power cables.

I have 2015 MacBook Pro 15".

Problem started with one monitor after 2 weeks of use and now week later, second monitor started to do same thing.

I already returned first one to the shop (warranty), no answer yet.

Did anyone ever find a solution to this issue? I am having the same problem. The monitor randomly does not wake up from sleep, and the power button is unresponsive. The only thing that works it to unplug the monitor from the wall and plug it back in again. Do we think this is an issue with the monitor or the mac? I have a MacBook Pro (Retina, 15-inch, Mid 2014) running Yosemite 10.10.4 (14E46).

I have the same problem. I take the power to the screen to make it wake up again. I'm quite sure that this is a common thing with this display, also on microsoft surface computers, as i've seen during some research.

This doesn't all the time but when it does its a real pain in the butt. I'll add I have to also unplug the HDMI cable from the monitor and let it sit for 30 seconds before things start working again. I've tried multiple cables with both HDMI and DVI and I was never able to figure out what the trigger was. I'm going to start tapping the monitor power button before I leave from now on. Oh by the way that's running 10.11.2 on a 2015 MBP 13".

I had a similar problem.

But what worked for me was:

on the monitor, go to the "menu", choose "others" then on the "DDC/CI" option, change to "Disable" instead of enable

hope it works for u guys too