If a Chrome extension is disabled you will see a warning icon in place of the Chrome 3 dot settings button:
Normal Chrome Settings Button 
Chrome Warning Icon
Click on the warning icon to see which extension needs attention
In this case, Equatio is disabled. Click on the message "Equatio - Math made digital is disabled" to see what needs to be addressed
Equatio needs to have permissions accepted. This will occur when an update is released for a Chrome extension that required users to update granting permissions.
Click Accept permissions and that will then activate the extension