I've had a Vixia HF R82 for a few years and have used it successfully. Now, however, I can take video and see it in the display window, but when I connect the USB to my Mac, the screen goes black and doesn't download. I've worked with Apple, and they've determined their new software is not the problem and suggested I contact Canon to see if something needs to be upgraded or if its broken. Thanks!
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Since updating to OS X 10.15, then to OS 11 and now OS 12 Monterey, Mac has moved to 64-bit architecture over the older 32-bit, so it is possible that has presented an issue, but one thing I would ensure are that the camera is powered on and in the Playback mode before connecting via USB. Next I would check to see if the footage/SD card are visible in Mac's Image Capture software.