I bought a Dell P2417H monitor just very recently. And connected it to my Macbook Pro 2012 this morning using a MiniDisplayPort to HDMI adapter and HDMI cable to the monitor. It worked just fine, and I could use the monitor as an external display. Then when I restarted my Macbook, the monitor suddenly just doesn't work.
It says: "no hdmi signal from your device".
I have tried everything. From unplugging and plugging, hard-reset, holding 30-seconds, doing PVRAM and SMC reset on my Macbook, doing the 'integrated/discrete/dynamic" thing, updated my firmware. OS X El Capitan by the way. I even talked to a very helpful Apple customer service officer for an hour to check all my OS software is fine.
Any advise? Still not working. What bugs me is that it worked just fine before I restarted my mac - can't figure out what's wrong.
The fact that it worked before you restarted the MacBook means something changed on the MacBook end. What it could be, no idea.
Does the P2417H pass its stand alone BID (Built-in Diagnostic), page 55?
This monitor was only validated/tested by Dell using Windows 7/8/10. Is there a Windows computer to test this P2417H on?
You should also ask the Apple users on their Forum for troubleshooting opinions.