Are you sure the LED is conencting to ground? Also, the voltage on pin3 of IC3 is looking fairly low. With a measured supply of 8.4v it should be more like 4v, not 2.4v. So, have a look again at R22, 23 and make sure they are right. If so, pull IC3 from its socket an remeasure pin3 without the IC to see what you get.