No signal at 2560x1440 resolution from early 2013 Retina MacBook Pro I have an early 2013 Retina MacBook Pro running macOS Sierra 10.12.5 connected to an ViewSonic VX2478 monitor using a MiniDisplayPort cable connected to a ThunderBolt port.  The monitor is detected correctly as having a default resolution of 2560x1440.  However, when I set it to the default resolution the monitor claims to have no signal while macOS seems to think everything is fine.  If I set the resolution to 1080p the display works fine.

When I started trying to make this work I had El Capitan instead of Sierra.  The problem was slightly different.  The monitor didn't display a "No Signal" error, but it didn't display anything, either.

I connected the display to my Windows laptop using its ThunderBolt port and the full native resolution worked fine.

I have tried the following:


Both a mini-DP to DP (included with the display) and a mini-DP to mini-DP cable (purchased new)
Reseting NVRAM
Reseting the SMC
Both Thunderbolt ports
Experimenting with various resolutions using SwitchResX
Disabling Automatic Graphics Switching


I haven't tried using an HDMI cable because I can't seem to find one lying around, and many of the solutions I've found to similar problems involve using a DisplayPort cable instead of an HDMI or DVI cable.
I solved this problem by using an HDMI cable.  Full resolution works fine.  I still don't know why DisplayPort doesn't work at full resolution.