For some reason mine also sometimes seems not to beep but will start, or sometimes not. Turns out the beeper seems to be an issue, if you listen well and it's really quiet it does actually very faintly beep then start, or faintly give error beeps. Haven't found any rhyme or reason, sometimes normal loud beep, sometimes really faint. Not sure if this is your issue and you can't hear the error beeps but that's my experience.
Maciej