IMHO, your rates / experience were probably too high for what they were looking for. Note that "high" does not mean your specific rates are too high, but that s

IMHO, your rates / experience were probably too high for what they were looking for. Note that "high" does not mean your specific rates are too high, but that startups generally pay poorly & they found someone cheaper. Other than that, people are really busy (especially if they're high-ranking like you say). You can always send a follow-up email a few days later confirming if they had received your last email & play the "I'm trying to lock in my availability for the next few weeks" card.