I am using Canon EOS 5D Mark IV and Lighting 5.7.1 on Windows 10 OS. As of a few months ago, I am no longer able to download RAW files. If I'm reading my LR program correctly, it shows Camera Raw 8.7.1. I haven't specifically downloaded this app so this is new to me. What can I do in order to read RAW photos from this camera into LR?
Did you get a new camera? The Canon 5D mark IV was first supported in Lightroom 6.7 /CC2015.7 (https://helpx.adobe.com/camera-raw/kb/camera-raw-plug-supported-cameras.html), so your version of Lightroom has never been able to import its raw files. The only way to open its raw files in your version of Lightroom is to download the free Adobe DNG Converter and convert them to DNG.