I recently bought a new power adapter off Amazon, and it worked with my mid-2014 MBP at work and my colleague's mid-2014 MBP, but not my mid-2012 MBP Retina 15" (which, frustratingly, it was bought as a replacement for). The green light comes on, but doesn't switch to orange to indicate charging, nor does the machine detect it.
It's literally the exact same model number of the adapter that came with my machine. I figured the replacement was possibly defective, so returned it and got a replacement. Alas, it still doesn't work on my mid-2012 MBP, but does work on my partner's mid-2014 MBP.
I've tried resetting SMC, to no avail. Even more confusing, my work power adapter charges my mid-2012 MBP fine, and is what I'm using at the moment.
Any ideas?
Edit: As requested, here are some photos of the sides of the new adapter.
Best Answer
You have the wrong power adapter.
The Mid 2014 uses a 60W adapter and the Mid 2012 uses an 85W.
See this page Find the right power adapter and cord for your Mac notebook on Apples's website for details
You can always use a power adapter with a higher power rating on a machine that requires less, but you can't use an adapter with a lower power rating on a machine that requires more. In other words a MBP with a 60W power requirement will work fine with an 85W adapter, but a MBP with an 85W power requirement will not work with a 60W power adapter.
This is the product you want.