I take it you added the crouch and prone animation and you didn’t set them up correctly.
I’d need to know if you did it using BPs or code to give you specific help.
Generally this is how it works. You will want a variable, probably a boolean, to indicate if the player is prone/crouched or not. On this Boolean you will want to add an OnRep notifier. Then in the function that is called to change the player to a prone/crouched state you want to do a check to see if it’s the client or the server trying to run the function. If it’s the client, you want to just call the same functionagain but on the server. The server will then set the boolean for that player. When that variable is changed the OnRep notifier is triggered. You will have to write a function for the OnRep notification. This is where you want to play the animation.
Let me know if you need more help