second MBP Time Machine not recognizing shared drive

All,
I have set up an external drive to my AEBS via USB, set it up to share via accounts, and then located the drive using 2nd MBP under 'Shared' and am connected. The problem is when I go to select that drive for Time Machine it does not see it. I can drag and drop files onto the drive via the finder, but Time Machine is blind to it. Any suggestions?

 

then again

So just as the odd screeching noise your car is making miraculously goes away just as you pull into your mechanics shop, I randomly changed the preferences to 'connect using AEBS password', and now it works fine. I was using 'accounts' because it was advised by a user from this forum but it now works so I'm not touching it.

Thanks anyway all.