To reproduce:
1. Make a fresh project.
2. Change player settings to deferred rendering.
3. Add a point light, set to soft shadows.
4. Add some geometry to the scene and note that shadows are working fine.
5. Change Main Camera to orthographic projection.
6. Check the point light in the inspector, note there is now a warning "only directional lights can have shadows in forward rendering" and shadows are no longer working.

Expected result: Shadows get rendered properly
Actual result: Objects have no shadows