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 2560×1440. 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.
Best Answer
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.