Make sure you are using the most up-to-date version of Gmail: Clicking on the gear icon in the top right corner of any Gmail page will take you to the "Settings" page, where you can see which versions of Google Mail are supported by your computer (and which features are available). If you're not using the latest version, upgrading is easy: just click on the three lines in blue at the bottom of any Gmail page, select "Update now," and follow instructions!