Microsoft has announced that it will no longer make the Office for Mac 2011 installer available through Office 365 after September 22nd. If you would like to get a copy of the installer before that date, you can head to the My Software page of the Office 365 Portal.
Office for Mac 2011 has been succeeded by Office 2016 for Mac. It is vastly superior, in my opinion, and thankfully merges the Windows and Mac versions to be very similar. Office 2016 for Mac requires OS X 10.10 or later though, so if you have an older device that cannot update to macOS 10.10, you might still be stuck with Office 2011.
Microsoft’s announcement in the Office 365 Message center:
Office 2016 for Mac is the recommended version of Office for Mac and includes all the latest upgrades and new features. Beginning September 22, 2016, Office for Mac 2011 will no longer be available for installation from the Office 365 portal.
How does this affect me?
Your users will no longer see Office for Mac 2011 as an option for download through the Office 365 portal. For users who already have Office for Mac 2011 installed, Microsoft will provide customer support and troubleshooting through October 10, 2017.
What do I need to do to prepare for this change?
We recommend users install Office 2016 for Mac to have the latest and greatest features and support. To install Office 2016 on your Mac, in the Office 365 portal, go to Settings > Office 365 settings > Software. Note: To install Office 2016 for Mac, you must be running Mac OS X 10.10 or later. Please click Additional Information to access the Office 365 portal, and get Office 2016 for Mac.