UFUNCTION(reliable, server)//set this to a server function
void ServerShouldSprint(bool bSprint);
void ServerShouldSprint_Implementation(bool bSprint); //<--- You have this function too? This is described in Cedric's PDF.
The _Implementation method is the one that is actually defined in the .cpp
Hmmm…just thought of something.
You need to be sure the below include is setup. I put mine a header that is included in every cpp.
// This is NOT included by default in an empty project! It's required for replication and setting of the GetLifetimeReplicatedProps
#include "Net/UnrealNetwork.h"