What camera model?
What happens when you try? Describe in detail. If there is an error message, please quote the exact unedited word-for-word error message.
Which camera(model) are you using.?Check if it is here https://helpx.adobe.com/creative-suite/kb/camera-raw-plug-supported-cameras.html
Check the version of Camera raw installed from Lightroom >>About Lightroom 6/Help>>About Lightroom 6