You have some Active directory users that have more than 1000 attributes. Your Active Directory user accounts don't meet ...

You have some Active directory users that have more than 1000 attributes. Your Active Directory user accounts don't meet the requirements for directory synchronization.  You can see a list of these users by opening Windows explorer and reviewing the files in folder Office365logs on your computer. Click on the link 'get help fixing this issue' in the actions pane located on the right side of the screen for assistance.