I have one child, born by ELCS, and like you, my milk never came in after the initial colostrum, despite immediate skin to skin, no health problems, taking all possible advice from LLL, midwives, HV, NCT lactation person, GP blood tests etc etc. No one ever came up with an explanation.
I'm sorry it happened to you, too - I found it unbelievably miserable. I was all set to deal with pain, latch problems, cracked nipples, tongue tie etc, but I didn't ever even get to try!
Sorry to have no advice, but no one ever explained it, and all the professionals were baffled. If I were to have another child, I would bear in mind that it might happen again, but that it would be through no fault of mine, and resolve not to beat myself up about something I couldn't help.