Have you checked to make sure the fire button is popping back up when you release it? Sometimes they get stuck down. Other than that, I've not heard of anyone resolving this sort of situation without taking the device apart and playing with the electronics, which takes some background knowledge. I'm afraid the device is probably dead (and not very safe).
For future reference, your problem is actually with the mod, not the battery. The battery forum is for actual battery cells. You have an internal battery, so the confusion is understandable, and you're by no means the first person to make that mistake.
Since the minifit is a pod mod, I believe you want to be here:
Vape Pod Systems A mod will probably be along to move the post before too long.