If they were stored bare root in a cooler at the nursery, that would account for ‘a’ delay, but they’d eventually begin to leaf out and grow…  How long have you had them in the ground, and how were they stored before you purchased them; bare root or potted?

I’ve heard of uninsulated semi truck loads of bare root fruit trees dying after passing over the Rockies due to having been frozen, thus some nurseries will not deliver orders on the opposite side until later in Spring.  The only mail order trees I’d received that ‘didn't leaf out’ were basically DOA (dead on arrival), the nursery refunded my money and I found replacements locally.

If they don’t send out leaves for an entire season, they’re gonners