You might see an "invalid certificate" error when installing Office 2016 for Mac, Office for Mac 2011, or Lync for Mac 2011. This occurs because a few of our install and update packages are signed with an older certificate. You'll simply need to download a package for a newer version, which uses an updated certificate, to use for your installation. This error does not impact your license or subscription.
Note: If you're an admin and your installs are failing, an invalid certificate may be the cause.
Update your certificate for Office 2016, Office 2011, or Lync 2011 for Mac
When you see this dialog box, click Cancel.
Download the package for the newer version, using the links in the following table.
Package with the older certificate
Download this newer version
Office 2011 Volume License packages (build 14.4.3) that were downloaded from the Microsoft Volume Licensing Service Center (VLSC) prior to March 8, 2017 (all languages)
Office 2011 14.7.1 Installer for Italian and Norwegian
Office 2011 14.7.1 Combo update for German, Japanese, and Polish
Lync 14.4.1 installer
Office 2016 15.28.0 Full Updater for OneNote
Office 2016 15.28.0 Full Updater for PowerPoint
Excel 2016 15.27.0 Standalone Installer
Open the update from your Downloads folder. Click to install. You're good to go!