Both HPCL-2231 optoisolators were replaced.

After re-inserting the servo card, I checked that the laser was on and that the NPRO noise eater was still happy.  The laser MEDM screen indicated both.  When I pulled up the ISS screen the power on the photodiodes was zero.  I checked the PMC screen and it indicated that there was no laser power incident on the PMC.  A closer look at the laser screen indicated that the low power shutter in the laser had closed.  Resetting the external shutter request from the laser MEDM screen restored the light.

After locking the ISS servo, everything seems okay as far as the laser goes.