I just had trouble with my JuiceBox 40. It would charge the Jeep always, but would constantly flash yellow after completing the charging. So it would go solid green after the Jeep was fully charged, then after a day or 3 hrs or 2 days or 8 hrs, basically some random amount of time afterwards, it would start flashing yellow which means it lost contact with the vehicle. I exchanged mine for a refurbished unit that is now working as it should. It also plugs into the Jeep port much tighter than the original one I had.
Check your port for obstructions and for bent pins. Also check the JuiceBox plug for obstructions and toggle the button you push to release the plug. That button on my original seemed to be the culprit on mine. If I pushed it about 20x before plugging in, it wouldn’t flash yellow as fast after charging. Also reach out to JuiceBox support for help. Good luck.