Bare root trees have been in refrigerated storage for months, and that makes them think it's deep winter. The trees already in the ground are aclimitized to the
local weather. Just be patient. As long as you see green cambium, the tree's alive.
I've been told that the sawdust the mulch the bareroots with is treated with some kind of sprouting inhibitor, so there may be lingering effects of that too. Don't give up, it will happen.