Japanese Elm

Question

This year it came back with only the lower branches budding. The rest of the tree is still dormant.

Answer 1

Is this a new planting?
I would go ahead and test the branches to see what is still alive and what may have died off. Branches and stems that bend are still alive. If they break or snap off, this part of the tree has died.
If the stems are still pliable, give the tree more time.

You can also do the scratch test on the bark.

Here are some links that will help you.

https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-scratch-test.htm

https://www.ag.ndsu.edu/trees/handbook/th-3-115.pdf