I'm having this problem too seems too much like a coincidense. However my solution was to wiggle the connector near where it connects to the laptop. By tilting the cable down a bit toward the back the charge light came on. I have all quite new clean equipement. 15" Powerbook Retina and using the Mag2 adapter. Note I tried flipping the adapter around and that made no difference. It's only when I pushed the cable down at the back that it started to work. I have the display connected to the thunderbolt near the power connector.
Model Name: MacBook Pro
Model Identifier: MacBookPro11,3
Processor Name: Intel Core i7
Processor Speed: 2.3 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 16 GB
Boot ROM Version: MBP112.0138.B02
SMC Version (system): 2.19f3
Thunderbolt Display:
Display Type: LCD
Resolution: 2560 x 1440
Pixel Depth: 32-Bit Color (ARGB8888)
Display Serial Number: C02LL2D0F2GC
Mirror: Off
Online: Yes
Rotation: Supported
Connection Type: DisplayPort