Turn Vamo verticle and shake it up and down,if battery is loose itill rattle,if this happens streth the bottom spring a little.
Some have reported that the contact button in the 510 gets pushed down by some tanks / catros , f thsi is the issue then nudge it up a little with a very small late blad screw diver working your way around it,be gentle.
I have three Vamos ,a V2 and two V3s and the first thing I do each time I place a tank on any of them is check resitance reading which will varify the connection. Some use a 510 to 510 connector / extension. Oe feacture which I really l9ke about the V3 is the removable top ring as use a lot of Evods and they have a nasty habit of the Ego threads sticking to the Vamo threads and then the tank unscrews from the base which make a mess unless Vamo is held upside down during removal. Removing the top section lets one tighten and lossen by the base whic I eel provides a better feel than using the tank does.
I do realize trhat it has a 10 sec. timeout per fire button press?
My V2 deeloped an intementant firing button issue which I fixed by removing battery extension tube and spaying switch / PCB with short blast of DexoIT D5 whic is an excellent contact cleaer / conditioner which I have used for many years on all types of electronics.