Hey Member, I have been having sync issues for about 4 months now (5.x.x for Mac) and I finally got it sorted out! You might have a file/note that is too big to sync. The new Evernote mostly sucks and never told me what was causing the error. I have un-installed, re-installed and even tried a few different older versions. None of that worked. (fierce rage!) I have tried several times in the past few months but got so frustrated that I gave up. Earlier today, I decided to go really old with some versions from a year or more ago. I still had the same problem but the error message was different with the old version. It told me that I had a note that was too big to sync. This was a notice that I had never gotten before with 5.0.x or anything later. This was the sync error that I got with the old version for Mac. Finally I had some sort of idea as to WHY it wouldn't sync. I moved the note in question to my desktop and now (after months of headache) I am back to normal syncing across all of my devices! YES!