Tell us what happens. Give us the details. If there is an error message, please quote the exact unedited word-for-word error message.
Also state your version NUMBER of Lightroom (we need the NUMBER and not words like "current" or "up-to-date")
The most important thing to know is the version of Lightroom that you are using. If you use a pretty old version, it may not support Canon EOS-7D CR2 files yet.
It would have to be an REALLY old version. That camera model has been supported since version 2.6.