Xamarin.InAppBilling fails to connect

I'm trying to use the InAppBilling component but the OnConnected handler is never called. At this point I'm just trying to verify that I can connect, so this is all the code so far:

mServiceConnection = new InAppBillingServiceConnection(this, publicKey);
mServiceConnection.OnConnected += () => Console.WriteLine("connected");
mServiceConnection.Connect();

"connected" is never printed to the console, and I tried putting a breakpoint there but it was never reached. I do get this warning when I test on my Nexus 7, but not when I test on my Galaxy Nexus:

[ContextImpl] Implicit intents with startService are not safe: Intent { act=com.android.vending.billing.InAppBillingService.BIND } android.content.ContextWrapper.bindService:517

Any ideas why it can't connect?