Cannot build for PlayBook

I'm trying to install an AIR mobile (flex) application on BlackBerry Playbook.

I managed to publish many successful builds of my app for all Blackberry devices EXCEPT Playbook.

The application failed to installed with this following error message "failure 821 Application-requires-system :unrecognized system name "BlackBerry10".

I am using FlashBuilder 4.7 with AIR 3.1 SDK and I am using Adobe and Blackberry ANEs to build the app.

Is the AIR SDK I am using (3.1) is correct for Playbook ? It DOES work for all other BlackBerry device.. ? Any ideas what might cause this ?

Thanks !