Intent not working - Activity not found

I have three intents to switch layouts etc.

Only the first seems to work and the other two are from what I can see, identical. I don't know if I have been staring at this for too long now and I am missing something stupid. Any suggestions?

Before anyone says, I've changed the actual package name etc to com.mysite.myapp. The originals are all spelt as I need them to be.

From my MainActivity

public class MainActivity extends Activity {

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

Button general1 = (Button)findViewById(R.id.btngeneral);
            general1.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent i = new Intent("com.mysite.myapp.general");
                    startActivity(i);                   
                }
            });

        Button health1 = (Button)findViewById(R.id.btnhealth);
            health1.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent i = new Intent("com.mysite.myapp.health");
                    startActivity(i);                   
                }
            });

        Button navi1 = (Button)findViewById(R.id.btnnavi);
            navi1.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent i = new Intent("com.mysite.myapp.navi");
                    startActivity(i);                   
                }
            });

The first one there works totally fine as expected it should.

This is from my manifest:

<activity
        android:name="com.mysite.myapp.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity
        android:name=".general"
        android:label="@string/app_name" 
        android:configChanges="orientation"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="com.mysite.myapp.general" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".health"
        android:label="@string/app_name" 
        android:configChanges="orientation"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="com.mysite.myapp.health" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

    <activity
        android:name=".navi"
        android:label="@string/app_name" 
        android:configChanges="orientation"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="com.mysite.myapp.navi" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

The class of the working intent

    public class general extends MainActivity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.general);
        }
}

The classes of the two non working intents

    public class health extends MainActivity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.health);
        }
}

and

    public class navi extends MainActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.navi);
    }

}

I hope someone has some good suggestions as I've been staring at this now for far too long.