Hey @cgwooky ,
I had a look at your file,
1. Your render engine is set to Cycles, instead of Eevee.
2. You have a light path node plugged into the color socket of the emission node of the sun.
3. Your tree material, has None selected for the shadow mode in the materials settings. You can change this by selecting the tree object, go to the material tab in the properties panel, scrolling down to settings.
It maybe worth revisiting the tree material and its settings.
Hope this helps
