I don’t believe the powerbank do 12v on USB.
The USB standard is 5v output.
Otherwise this powerbank would fry any device which use USB. (5v in)
If this powerbank is DIY and you build in an usual USB connector it’s also a bad idea, only USB gen2 allow 3A max.
Change output connector to the usual low power connectors as you have at your camera.
Maibe charging is 12v, but never the output due to the above reasons.