Controlling 2 WS2812b strips with a NANO and 3 buttons

Other Hardware LEDs and Multiplexing
16

Sorry : my mistake. Change the line

bool StateB2 = digitalRead(PIN_BUTTON1);

to
bool StateB2 = digitalRead(PIN_BUTTON2);(PIN_BUTTON2 instead of PIN_BUTTON1).
It should be OK now (fingers crossed)