Nope, can't spot the fault just now, but you have a dangerous blunder in the PCB pattern design; you have a trace passing under the MOC3041. You should never have a trace under the optocoupler, in fact the PCB should instead be slotted under it and for at least 5 mm on either end. The trace should instead have been run under R3.
That said, there is no obvious answer to your problem - the circuit should work just fine; either there is a defective component (cheap eBay?) or you have dirty (wet; conductive) flux between critical points.