1. Check the quality settings of the game. Under certain quality conditions, shadows may be turned off to improve performance
2. Check whether the light has turned on the function of casting shadows
3. Check whether the objects in the scene have turned on = the function of casting shadows
4. If you find that direct light cannot produce shadows, everything else is correct, and the following error is reported, then set the following options in Graphics to Built-in Shader to solve the problem
Shadow map cache entry with NULL shadowmap?