try add UPROPERTY()for your variable,and replicate your struct var like this
//your_struct.h
USTRUCT(BlueprintType)
struct FMyStruct
{
GENERATED_BODY()
UPROPERTY()
float my_float=0.0f;
UPROPERTY()
int32 my_int=0;
};
//your_character.h
UPROPERTY(Replicated)
FMyStruct mystruct;
public:
virtual void GetLifetimeReplicatedProps(TArray<class FLifetimeProperty>& OutLifetimeProps) const override;
//your_character.cpp
void AYourCharacter::GetLifetimeReplicatedProps(TArray<class FLifetimeProperty>& OutLifetimeProps) const
{
Super::GetLifetimeReplicatedProps(OutLifetimeProps);
DOREPLIFETIME(AYourCharacter,mystruct);
}
(my english is not good:<)