Q.I planted a Stellar Pink Dogwood tree last April. This year the branches are pliable — not dry and brittle, but there are no
leaves on the tree at all. Should I replace the tree at this time or give it another year? I live in Iowa, zone 5. The tree is planted in full sun.

Certified GKH Gardening Expert
Some sites list the growing zones as 5 to 9 but some say 6 to 9, so you are right on the edge. If your winter was below normal the tree may have had some root dieback. It's possible it could slowly recover; but it is just a waiting game. I would add a good amount of mulch at least 3 feet out from the tree to help it through the next winter as well as provide much needed moisture this summer.
You can contact the garden center; most reputable sellers will replace a tree within a year.
https://www.gardeningknowhow.com/ornamental/trees/dogwood/growing-kousa-dogwood-trees.htm