Outlook for Mac 15.3 (Outlook 365) gets hung up on Sync Pending

I have the same issue, I ended up downgrading back to Outlook 2011.

Same issue here.  +1.  Says "Sync pending for this folder" but activity shows nothing is happening!

It's really bad and sad when Apple can produce an Exchange client that's more reliable than Microsoft.  Had nothing but trouble and had to give up on Outlook 2011, Outlook 2014 is even worse -- it won't even fetch email!  

If I restart Outlook the mail finally arrives.  But this is a disaster.  I can't afford to have email stop working in the middle of the day and suddenly have it wake up and send me with a barrage of emails from the last 3 hours that it only now decided to deliver!

Edit: Grumble... turning Apple Mail back on and deleting Outlook 2014....

I have the same issue, I ended up downgrading back to Outlook 2011.

Progress made, 

I followed the lock file process described earlier but that alone made no difference.

So I went back and removed all links to other shared calendars, then went back to the lock on the file. 

I had to remove the entire reference to the OWA address as well as the EWS/Exchange.asmx portions of the server addresses.  Ultimately the address line is https://servername.domain.com then locked the file in "get info".  

the process of both portions somehow I got the instance of Outlook 365 to pull mail. it delivers about 5-10 minutes after my iPhone but I am getting the mail.  

Still no shared calendar function which defeats the purpose of the instance of Outlook on the Mac.  The Mac Calendar works perfectly. Sad to be MS. 

When did software become acceptable to kinda work?

Same issue for me as well. Very frustrating. Makes the new Outlook very painful to use.

I am also having this same problem.  It's a shame because the new Outlook looks nice and integrates into the notification bar.  In the meantime, I've switched back to Outlook 2011 and Apple's tools.

Hopefully somebody from MSFT chimes in soon.