Iphone 6 stuck in DFU mode, Device cannot update from recovery or update option - Activation Lock

iPhone 6 A1549 is stuck in DFU mode.

Iphone had activation lock due to buying it online and not being able to contact owner for the **** code to activate it.

I tried putting it in DFU mode and downgrading the firmware to 10.3 ipsw.

My iMac then started extracting software from the iPhone and once completed that step - it should install the ipsw (from what I remember) but it gave me an error code and said that it could no longer find the device. I tried this twice on my iMac and then once on my MacBook.

Now the iPhone is stuck in DFU mode, recovering/updating to current firmware didn't even work.