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Time machine not working after upgrade to Sierra even after adding afp address of time capsule and reformatting. Checked activity monitor. Other El Capitan machines can access TM just fine.
MacBook Pro with Retina display
Since upgrading to 10.12.2 (16C67) my time machine has started working.
UPDATE:
This problem was occurring on my Macbook Air (13in early 2015) after I upgraded the OS to Sierra 10.12.2 and using my LaCie external hard drive (Porsche design, 1TB, 2014ish). It was stuck on "preparing to backup" for about 20 minutes but it finally kicked on and is working with my Time Machine. I'm probably not the first person to figure this out, but thought it would be helpful to contribute.
Time machine not working after upgrade to Sierra
