Android App not appearing on Google Play for certain devices, why?

I have two clients who can't download my app. I can see and download it perfectly but for them it either doesn't appear, or says that the device is not compatible.

Things that I've tried: - Cleaning the project and rebuilding each time - Asking the client to clear their Android Market cache - Updating my Android SDK's so I have everything up to 4.1 - Removing the minSdkVersion attribute entirely - Removing the uses-sdk node entirely

Here's my settings:

<android xmlns:android="http://schemas.android.com/apk/res/android">
        <tool-api-level>16</tool-api-level>
        <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="11"/>
        <manifest android:versionCode="15" android:versionName="1.25" android:installLocation="preferExternal"/>
</android>

I'm not sure and can't find it in any documentation what effect the tool-api-level number has on device compatibility.

In Google Play it says the following under the Supported Devices section, although I haven't put any particular declaration like this in Tiapp.xml:

This application is only available to devices with these features, as defined in your application manifest.
Screen layouts: SMALL NORMAL LARGE XLARGE
Required device features
android.hardware.camera
android.hardware.camera.autofocus
android.hardware.location
android.hardware.location.gps
android.hardware.location.network
android.hardware.touchscreen
android.hardware.wifi
This application is available to over 1064 devices.

When you use something like GPS or camera, Google Play takes this as a needed feature to use the application when maybe your app can run even if you don't have GPS on your device, so, you can exclude all or some of these features adding these lines between the <manifest> </manifest> in the tiapp.xml:

<uses-feature android:name="android.hardware.location"         android:required="false" /> 
            <uses-feature android:name="android.hardware.location.gps"     android:required="false" /> 
            <uses-feature android:name="android.hardware.location.network" android:required="false" />
            <uses-feature android:name="android.hardware.touchscreen"      android:required="false" />
            <uses-feature android:name="android.hardware.camera"           android:required="false" />
            <uses-feature android:name="android.hardware.camera.autofocus" android:required="false" />
            <uses-feature android:name="android.hardware.wifi"             android:required="false" />

These way, you are telling them that these features are not needed in order to use the app. Be sure then, to control this inside your app, for example, if you don't require camera, maybe you should check for it before using it and things like that.