I'm assuming you have an E-Power 14650 as it is the most popular model. There are two other E-Power models out there. Each is very different from the other.
A couple of answers could help to figure this out if you have the 14650. If not, never mind.
-Which E-Power 14650 switch module do you have? To determine this...
a. Color of button light?
b. Equipped with 5-click switch safety?
3. Operates LR cartos of 2.0 ohms or less?
-14650 battery. What was the battery charge voltage when you tried to fire it up?
-What carto or atty are you using?
a. Single or dual coil?
b. Resistance?
It's easy to install a substitute switch module.
1. Remove the cone and carto or atty.
2. Remove the battery tube and battery.
3. What is left is the switch module. Just put it back together with the new switch module.
Those OEM
batteries for the E-Power 14650 say Smoktech on the blue shrink wrap. Make sure the wrap is not cut or worn through anywhere.
Also, the PCB and base plates on these
batteries are often installed a bit off-center and/or the positive terminal is off-center or crooked. Sometimes turning the battery in the tube and screwing the tube back on corrects a bad connection to the battery contact on the switch.
The Trustfire Blue protected 14650 batteries don't perform any better than the OEM batts, but the build quality is much better. Tougher shrink wrap, too.