New user of contour 2- power all button on remote doesn't work.

XR11-RF is printed on the back of the remote

Same as mine.

If your Aquos is already paired, use Contour to pair your Panasonic.

Contour button > Settings (gear icon) > Remote Settings > Voice Remote Pairing > Yes > Choose Another Device > Find Panasonic

...this where I bailed because I don't have a Panasonic.

Before pairing with panasonic, TV POWER on tuirned on the TV. After pairing to Panasonic, TV POWER ON turns on the Panasonic. I have to use a seperate remote to turn on and off the TV.

I have tried pairing to the panasonic using the auto pairing Ino code) method AND I have tried pairing using the code COX's web site gave me. Same result.

I used that web page to get the entry code for both the TV and the Panasonic Stereo. 

"Auto Detect" would be under HDMI Audio Output but these options don't provide power control.  HDMI Audio Output only provides options for audio format (Stereo > Dolby) and choice of decoder.

It appears when OP pairs the TV and then subsequently pairs the AVR, the AVR code replaces the TV code.

If OP correctly followed the procedures within Contour (Voice Remote Pairing), the Panasonic code should have been stored with the TV code...not replace it.

I suspect a faulty remote.  If there is a procedure to completely "blank" the remote from the Contour receiver, TV and Panasonic; it'd probably help reset the instruction set.  However, it'd probably be easier to just exchange the remote.  Don't cost nothing.

procedure to completely "blank" the remote

Same equipment, same procedures...different provider, more cogent steps.

Look for Factory Reset...(XR11)

www.xfinity.com/.../remote-xr2-or-xr5-buttons-do-not-work

Did that under direction of tech support the first day I got the system. No difference. Once I put in the Panasonc code, it overwrites (?) the TV code. 
ALSO ALL POWER ON BUTTON does NOT work at all - the contour box never shuts off unless I push the on/off button on the top of the contour box.