Hello

This looks like San Jose scale insects on he bare branch section. The round grey scales protect the insects underneath which feed on the tree sap.

Here is management information for you.

https://hort.extension.wisc.edu/articles/san-jose-scale/

Since the tree is ornamental, you need not be concerned with using chemicals safe for edible fruit trees. You can treat the tree mid-June as outlined in the above link. Be sure the product is labeled to control scale insects.

Here are details on how to use horticultural oil.

https://content.ces.ncsu.edu/san-jose-scale-1

As for the bare spot, once the scale insects have been treated, allow the branches to grow around it and perhaps gently tie some longer branches toward or over it, training new branches to grow over the bare spot. This will take a2-3 seasons of growth.

Treat the tree again next spring just before bud break as outlined in the above links. Monitor the tree each year for new spots with scale and treat if necessary. Also, please read and follow all directions and precautions on any chemical product you use.