I was searching online and found this old thread. I have 3 older stealth cams. Model 1530IR. Same problem on 2 out of 3.
Will not work with a fully charged external 12 volt stealthcam battery pack.
Will only work with the internal C batteries.

Has anyone got a definitive answer as to the problem? Could it be where the barrel plug connects to the inside of the camera?

I know it's an old thread but if you have any idea of the resolution I would like to know

Thanks