You need to set your Pitch variable inside of your character blueprint to replicate. You might also need to set the pitch variable inside of the animation blueprint to replicate.
I replicated both for the time being, and it works ok
I also do the math on the client side before doing the RPC call. Also, the RPC call takes my character class which for now is just ThirdPersonCharacter, and the Pitch float variable.
I then set the ThirdPersonCharacter’s pitch value again on the server side.