Battery problem

Hi, I’m building my first s500 drone. I bought this battery Turnigy 2200mAh 3S 20C. Everything worked perfect, the RPI and NAVIO2 turned on correctly. However, now they do not power on (if I connect it via battery). I do not know what happened, the charger looks like this:

I think a cell does not work. Can this be the reason why NAVIO2 does not turn on when I connect it to the battery? To make it clear, NAVIO2 works if I connect it via USB.

could you measure the voltage of each cell through the balancer cable and report?

Yes, I measured it with a Lipo battery low voltage teaster. The results are: no.1: 4.19, no.2 4.14. no.3 does not appear.

hard to tell without knowing if your measurement method also makes a slightly undervolted cell “not appear”

but if your power module does not power navio at all anymore (8 volt should be sufficient) - your battery (actually cell nr 3) might be severely damaged (and is “open circuited”; actually never experienced that before with my lipos - even with extremely and visually damaged lipos);
don’t charge it without a close eye for heating and swelling and I’d suggest investing in a new battery for flying…
better also store it in a fireproof place…

if it’s a new battery and you didn’t mechanically tortured it or totally discharged it I’d contact the seller…
however navio2 should be fine

Do you have a multimeter to meassure the voltage at the power connector of the lipo?