Q.Is my dogwood lost?
My white flowering dogwood is over 19 years and always did great. But this year I haven’t seen a single leaf yet. I see no signs of disease and I have Some green branches. Only thing that’s changed is it gets more sunlight? What can I do to help it?

It doesn't appear to have any growth.
Check the branches; do the bend or snap off?
You can do a scratch test.
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-scratch-test.htm
A tree can die off do to pests, disease, environmental issues or for unknown reasons.