Oh, is that right?
I ran into this issue recently, while trying to send an Apple Push Notification Service message from a web app running in the context of IIS.
The issue is pretty simple and I have come across it a number of times, but in my old age keep forgetting what was the cause.
Well, for me it was the fact that the installed APNS certificate’s private key did not have valid permissions for IIS_IUSRS.
It would be pertinent to note, that giving permissions to ‘Everyone’ does NOT cut it, since IIS_IUSRS is not part of ‘Everyone’.