Compiler doesn't like my class C++. getting undeclared identifier error and more

I created a class called "Message". I want to store Messages that are created with the class "Message" in a static vector array in a class named "MessageBox". The compiler tells me that Message doesn't exist, but the editor is telling me otherwise. Here are the files with the code:

"Message.h"

#pragma once
#include <iostream>
#include <string>
#include "Message Box.h"

namespace ATE {
    class Message
    {
    public:
        Message(std::string act, std::string ID, std::string IDtwo) { action = act, ID1 = ID, ID2 = IDtwo; }
        Message(std::string act, std::string ID) { action = act, ID1 = ID; }

        std::string action;
        std::string ID1;
        std::string ID2 = nullptr;

    };

}

"Message Box.h"

#pragma once
#include <string>
#include <vector>
#include "Message.h"

namespace ATE {
    class MessageBox
    {
    public:
        static std::vector<Message> MsgBox;
        void addMessage(Message msg);

    };
}

"Message Box.cpp"

#include "Message Box.h"

void ATE::MessageBox::addMessage(Message msg)
{
     MsgBox.push_back(msg);
}

My errors:

Error C2065 'Message': undeclared identifier (file: message box.h, line: 11)

Error C2923 'std::vector': 'Message' is not a valid template type argument for parameter '_Ty' (file: message box.h, line: 11)

Error C2061 syntax error: identifier 'Message' (file: message box.h, line: 12)

Help is much appreciated (: