If you have another tank try that on your mod to see what it says. Other than that i can't really say what's causing the issue for you without actually holding the stuff in my hand.
If another tank works fine you got a shorted out tfv4 for some reason. This can happen sometimes and they don't last forever.
If you don't have another tank you can go to a B&M and ask them if you could try one of their tanks on your mod to see if it works and maybe let them take a look at your tank to see if they can find whats causing your problem.
Anyhoo good luck