Did you persist with th breastfeeding on Day 2? I suspect you waited too long to breastfeed and as a result, the engorgement set in by then. Colostrom should have come in immediately after the birth. With a C-section, this may take slightly longer but it should not be more than a few hours later.
I believe "letdown" only happens after the body stops producing colostrom and start producing milk. Did you try actually breastfeeding or did you only use the electric pump? However expensive the pump is, you should remember that it is never as effective as the suckling from a baby who has been effectively latched on.
For my case, I had lots of engorgement problems too, but from an over-supply, rather than a reduced outflow, so my problem was easily resolved, i.e. just express more often. The lactation consultant at the hospital recommended having the baby feed every two hours and alternating the breast when feeding. Of course, this is possible only if you have enough milk in one breast. Otherwise, you will have to switch to the other breast after 10 minutes or so. In your case, you may face engorgement problems because feeding or expressing every three hours may not be often enough.