Our site is missing viewport tag?
This tells the browser how desktop sites should be scaled for mobile devices.
<meta name="viewport" content="width=device-width, initial-scale=1">
This tag is not necessary for desktop devices so it is not added to the source.
Smart sites detect the device and therefore only add the viewport on mobile devices.
SEO audit tools may flag this as missing in reports, but it can be ignored as they are most likely rendering only the desktop source code.