So on line 96
if(SpecHandle.IsValid))
should be
if(SpecHandle.IsValid())
Also to preempt add the OnRep function to the attribute uproperty like so
UPROPERTY(BlueprintReadOnly, Category = "Attributes", ReplicatedUsing = OnRep_Health)
FGameplayAttributeData Health;
The ReplicatedUsing binds the OnRep function