Hi Olivia,
In Office 365, Office 2011 for Mac needs user’s credential to activate the product. Each day, or each time the user logs on to their computer, the computer connects to the Activation and Validation Service to verify the license status and extend the product key. As long as the computer can connect to the Internet at least once every 30 days, Office remains fully functional. If the computer goes offline for more than 30 days, Office enters reduced functionality mode until the next time a connection can be made. To get Office fully functional again, usually a user can simply connect to the Internet and let the Activation and Validation Service reactivate the installation. However, it’s an abnormal behavior if the Office keeps asking you to login. If you’re in this situation, please refer to http://support.microsoft.com/kb/2476507 to troubleshoot the issue.
About the data analysis toolpak, this issue can be related to the Office client and our forum doesn't focus on Office client issues, we can only provide limited assistance with it. For the Office client related issues, we offer a specific support channel for our users. You may get the professional support via the following link: http://answers.microsoft.com/en-us/mac
In addition, I have found a similar thread on the Office 2013 forum for your reference:
Thanks for your understanding.
Best regards,
Rachel