Why doesn't my android application show up in the launcher?

Question

I'm developing an application for the Android platform targeted for api level 4 (Android 1.6) but I can't get it to show up on my phone and I can't figure out why. Here's my AndroidManifest.xml is there a problem in here? Or is there something else I should be looking at?

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.sbe.app.hellocogen"
          android:versionCode="1"
          android:versionName="1.0">
            <uses-permission android:name="android.permission.INTERNET" />
        <application android:icon="@drawable/icon" android:label="@string/app_name">
                <activity android:name=".activity.ListPlants"
                        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=".activity.AddPlant"
                        android:label="Add Plant">
                    <intent-filter>
                        <action android:name="android.intent.action.VIEW"/>
                        <category android:name="android.intent.category.DEFAULT"/>
                    </intent-filter>
                </activity>
                <activity android:name=".activity.UnitActivity"
                        android:label="IP HERE, PLANT NAME">
                    <intent-filter>
                        <action android:name="android.intent.action.VIEW"/>
                        <category android:name="android.intent.category.DEFAULT"/>
                    </intent-filter>
                </activity>
        </application>
        <uses-sdk android:minSdkVersion="4"/>
    </manifest> 

When I started this application it didn't show up but I fixed it by setting the minimum api level to 4 instead of 7 then it started showing up but now it stopped showing up again and I don't know why.