GCM not waking up device

I developing a GCM application. Everything works fine when the device is not idle (i.e. sleeping by pressing the power button). However, when I send the message when the device is idle the device does not wake up.

I have done the following:

1. Verified that delay_while_idle is not set to true in the server app
2. Used a different collapse key for each message
3. Rebooted the device multiple times
4. Tried omitting the delay_while_idle completely from the server side - it has no effect

I am targetting Android 2.2 api level 8 (lowest version), testing on an actual device running Android 2.3.6

Device is using wi-fi, there is no sim card - but receives messages fine while running and not idle.

This is the client manifest permission section:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<permission
    android:name="com.tranwall.sdk.device.android.permission.C2D_MESSAGE"
android:protectionLevel="signature" />
<uses-permission android:name="basePackage.android.permission.C2D_MESSAGE" />
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE"  />           
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />    
<uses-permission android:name="android.permission.RECEIVE_SMS" />
<uses-permission android:name="android.permission.INTERNET" /> 

Thanks in advance for any help