Direto da Microsoft:
Office 365 is not designed to work with Office 2007 because Office 2007 left mainstream support on October 12, 2012. Office 365 does not offer code fixes to resolve problems you encounter when using the service with Office 2007. You should expect the quality of the user experience to diminish over time, and many new Office 365 experiences will not work at all. We recommend that you upgrade as soon as possible to Office 365 ProPlus or Office Professional Plus 2013 for the best experience with Office 365.