Your version is old enough that it may not work with the RAW update for those files
-Lightroom serial number will work on both Windows and Mac versions https://forums.adobe.com/thread/2179765
Download the free Adobe DNG converter, convert to DNG.
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Lightroom 4 version is not compatible with the Canon EOS 70D, you can try few things to get going.
1. You can upgrade your Lightroom 4 to Lightroom 6/2015 version and it will support the raw format for Canon EOS 70D.
2. You can download the free DNG converter 9.10 and you can convert the Canon raw images to DNG format and use it with Lightroom 4.
Check the download links
I have the same problem. I have Lightroom 5.7.1. When I tried to import .ARW files from my Sony A7RII, Lightroom first indicates that "Preview unavailable for this file". Then after I checked those files and imported them, I got a message "The files are not recognized the the raw format support in Lightroom".
Your camera was first supported in Lightroom 6.1.1.
Either pay to upgrade to Lightroom 6 then free update to 6.10.1. Then edit your Raw files.
Or join the Cloud (then free update to Cloud CC 2015.10.1). Then edit your Raw files.
Or convert to DNG then edit the DNG files in 5.7.1.
Lightroom version: CC 2015 
Camera Raw Prferences: 9.0
License: Creative Cloud
Can not import my SONY A7RII and A7SII .arw RAW files:
"The files are not recognized the the raw format support in Lightroom".
Thanx - it works.