You should have the same params on function and delegate. It is strange that you didnt had a compilation error.
Someting like this:
in .h
DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(FMySignature, bool, IsOk, AActor*, MyActor); //"," between type and variable name
UFunction() //do not forget that
void MyActor::Bar(bool IsOk, AActor* MyActor){};
FMySignature OnEvent;
in .cpp
OnEvent.Broacast(b, MyActor);