Player falls through the level in FPS tutorial

Hello,everyone, I have tried the FPS toutorial
I followed the instrution step by step exactly and have checked that the all components made up the floor have mesh colliders,but I found the player would fall through the level
I have tried to add Rigidbody, Capsule collider to the graphics of Fisrt Person Controller, but it doesn’t work.
If anyone has some sugguestion,please let me know.

When you place your object, make sure its sitting slightly above the floor. If the object is touching, there is a chance it wont pick up the collision before falling through.

Thanks your suggestion! In fact I have moved the player much higher over the ground, but it still falls through the level

Thanks for your suggestion. In fact, I placed the player much higher in the air, but it still fall through