I noticed the same thing today with my Nexus 6p when i tried to beam today. Android Beam is not working on my Nexus 6p. If anyone finds anything out, please post the fix.
The NFC transceiver on the 6P is at the top of the phone. So, for example, using Android Beam with my Nexus 5, the top of the 6P needs to be against the middle of the 5.
If you center the phones on each other, it doesn't work at all.
I beamed a selfie my husband took with his Nexus 6p to my Nexus 7 (2013) tablet with no problem. It took a little playing around to get positioning correct between the tablet and phone to trigger it but otherwise no issue.