Uh, we still don't know anything about what you're using, so any help has to be only generic.
Check coil usually indicated the
mod / pod sees NO coil, so clean all the relevant contacts. Try scrubbing them with a cotton swab dampened with rubbing alcohol, both the
mod and the pod sides. If possible, do turn OFF the mod. If not possible, be careful to not fire it while scrubbing.
Another possibility is that the contact on the mod portion has gotten pushed down too far to make contact, a common issue in the past. Fixing that depends on the hardware, and we know nothing about that.