What am I doing wrong with this LM393?
The part of your circuit to drive Q2 from the output of U1A looks OK, although there is no need for R10.  The current thru the base will already be limited by R8.  R10 will only slow down the transitions.

I didn't look up the LM393, but make sure that the open collector output is really with respect to the negative supply, which is ground in your case.  Otherwise, Q2 won't be reliably turned off, or at all.

If the output of U1A really isn't going high, first check that the supply pins are at the expected voltages.  You don't show what voltage VM is.  Check the datasheet and make sure this is high enough for the LM393 to operate properly.

Then check the input pins.  Maybe the bug is in not driving them to a state that should make the output high.