Be pushy with Push Notification in your game: Application Manifest File

First of all, you will need to enter a Publisher name in the Properties\WMAppManifest.xml file. 

Change the Publisher from two quotes to the following (carriage returns added by author), for push to work you must type in a publisher name, make something up:

 <App xmlns="" 

 ProductID="{781a18da-40e5-40ae-82e2-e7ce9ae8e1d4}" 

 Title="Trailer Trash JunkYard" 

 RuntimeType="XNA" 

 Version="1.0.0.0" 

 Genre="Apps.Normal" 

 Author="" 

 Description="" 

 Publisher="Trailer Trash">

 A little further down in the WMAppManifest.xml file you will see, check and make sure that the highlighted line, <Capability Name="ID_CAP_PUSH_NOTIFICATION" />
is contained under the Capabilities Tag:

 <Capabilities>       <Capability Name="ID_CAP_NETWORKING" />       <Capability Name="ID_CAP_LOCATION" />       <Capability Name="ID_CAP_SENSORS" />       <Capability Name="ID_CAP_MICROPHONE" />       <Capability Name="ID_CAP_MEDIALIB" />       <Capability Name="ID_CAP_GAMERSERVICES" />       <Capability Name="ID_CAP_PHONEDIALER" />       <Capability Name="ID_CAP_PUSH_NOTIFICATION" />       <Capability Name="ID_CAP_WEBBROWSERCOMPONENT" />       <Capability Name="ID_CAP_IDENTITY_USER" />       <Capability Name="ID_CAP_IDENTITY_DEVICE" />       <!--New Windows Phone OS 7.1 capabilities inserted during project upgrade.-->       <Capability Name="ID_CAP_ISV_CAMERA" />       <Capability Name="ID_CAP_CONTACTS" />       <Capability Name="ID_CAP_APPOINTMENTS" />
</Capabilities>