I install Outlook Mac 2011 and got the update from the Office 365 site. After that my Windows Outlook .pst file was imported. That worked and brought in emails and contacts from the old system. However, after a week or two there Outlook mac did not show any of the imported contacts. The .pst file was imported again but this time all the contacts went missing after just a day. 

Why does this happen? Any help is appreciated. 

Thanks,

Ken