Make sure you have everything set up on the android side. https://developer.android.com/google/gcm/gcm.html
Besides that, PushSharp does have a new version available that you may want to get. https://github.com/Redth/PushSharp
You may also want to add some events to track and make sure there are no issues.
push.OnDeviceSubscriptionExpired += new DeviceSubscriptionExpiredDelegate(push_OnDeviceSubscriptionExpired);
push.OnDeviceSubscriptionChanged += new DeviceSubscriptionChangedDelegate(push_OnDeviceSubscriptionChanged);
push.OnChannelException += new ChannelExceptionDelegate(push_OnChannelException);
push.OnNotificationFailed += new NotificationFailedDelegate(push_OnNotificationFailed);
push.OnNotificationSent += new NotificationSentDelegate(push_OnNotificationSent);
Then on the android side, check logcat to see if any messages are coming through.
Even stepping back and try to send a push from the device itself. https://developer.android.com/google/gcm/client.html