Yongnuo speedlite YN-560 II help

Hey

I just recently purchased this speedlite and i want to use it via wireless trigger. I bought a trigger that works with Sony and everything looks to be working. I'm a complete noob when it comes to using a flash wireless though, the Yongnou has 4 modes, M S1 S2 Multi. I dont know wich one to choose, i got 2 channels on my wireless trigger, it says 1+2 ON or OFF on both receiver and transmitter.

Problem is i can only get the flash to fire sometimes, and sometimes it just doesnt, anyone have any idea what could cause this inconsistency? i wait for beep sound to stop and then fire again.

Thanks in advance