Photon and Unity : Up down character movement when the seconde player join

I'm currently experimenting with photon in Unity and I'm trying to work with mouse click movement with an up down environment but I got an issue with that.

I can connect multiple players in the same room. The first one can move and the camera follow the player prefab as I would like to work.

But when the second player join the room, he is not able to move is character and I don't know why.

Here's my game manager script:

My player prefab is being instantiated when the players click on a button "Start".

Here's my character movement script if you need it:

Thanks for the help, really appreciated!

I'm new to Unity so any advice will be helpful