Does the APNs authentication key work for all my app ids?

"One APNS to rule them all, One APNS to find them, One APNS to bring them all and in the darkness bind them."

The answer is unfortunately yes. You can use one APNS for all of your IOS apps. Be careful while using it !

I see that the keys can be used for multiple apps. Still I'm having problems since I changed to the new .p8 type of key.

The Answer is Yes. One key is used for all of your apps.