Magsafe 2 85W charger will not charge 2015 MacBook Pro

I have an old 85W Magsafe 1 charger with a T-tip (yes, it’s an odd ball one) that I converted to a Magsafe 2 T-tip by resoldering a brand new Magsafe 2 T-tip cable. It charges all all of my laptops without issues:

• 2013 13” MBP Pro
• 2014 15.5” MBP Pro
• 2015 13” MBP Air

They all show light up solid green when charged up or solid amber when charging.

Unfortunately, the charger won’t power up my 2015 13” MBP which has the battery disconnected. The amber light on the cable blinks and then turns off. My other magsafe 2 chargers will at least power it up with a solid amber light. As a test, I tried at least three different chargers and they were able to power it up without issue.

I highly doubt I botched my conversion. Are there other differences either in the MBP 2015 Pro circuitry or the Magsafe 1 circuitry that may cause it not to charge.