Well I think it's the tester. I get no amps on my lavatube either.
It's a flashlight, 18650 battery, copper positive terminal wired to a madvapes horn switch to a madvapes 510 connector.
And it's showing solid 4 volts at the connector. But it actually fires a 3.2ohm atomizer. I will be using a 1.8 on this mod probably though.
Why do you say having 4 volts is an issue?