3.7v (1200MAh) lipo battery and Arduino MKRZero

I'm using 3.7v (1200MAh) lipo battery for powering the Arduino MKRZero but Arduino MKRZero doesn't turn on Why that happened? battery is charged.

also, I'm use "Solar Power Management Module, for 6V~24V Solar Panel" with 3.7v (1200MAh) lipo battery and Arduino MKR Zero... and Arduino MKR Zero doesn't turn on too.

Could anyone help me, please?