Q.Mongolia tree
We have two Mongolia trees. They are about 16 years old. One will not grow, seems dry. It appears to have no sap.can we help it.

Your tree may have a canker that is girdling the tree.
You may want to have the tree inspected by a qualified Arborist.
These links may have more help for you.
https://www.gardeningknowhow.com/ornamental/trees/tgen/dry-brittle-tree-branches.htm
http://plantsciences.utk.edu/pdf/Knoxetal_MagnoliaDiseases_Magnolia93-2013.pdf