Just upgraded to OS Sierra (v10.12) and my second display port no longer works.
Previously, I was using each display port to run a DELL U2713HM at 2560 x 1440 resolution (total of two external monitors, plus laptop screen). This worked perfectly with El Capitan.
Both monitors work individually when using the first display port, but when either are plugged into the second display port both screens (laptop and external) go black. Have tried resetting NVRAM and SMC, have also tried reinstalling Sierra. (Wish I could go back to El Capitan, but don't have a backup drive)
I can use the first display port and the HDMI port to run both external monitors, but the highest resolution option provided for the monitor on the HDMI cable is 1080p.
Machine Specs
MacBook Pro (Retina, 15-inch, Mid 2015)
Processor: 2.2 GHz Intel Core i7
Memory: 16 GB 1600 MHz DDR3
Graphics: Intel Iris Pro 1536 MB
MacBook Pro (Retina, 15-inch, Mid 2015), macOS Sierra (10.12)
