So i have macbook pro with windows 7 on it. And recently I got SD card 128gb and when I put it in the sd card reader on mac, nothing appeared. So i restarted and it worked and I saw the sd card.
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I had the same problem as you while using Windows 10 Pro on Bootcamp (on my MacBook Pro, Mid 2012) and I think I found a solution for you!
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I went into Programs & Features in the Control Panel (or just search 'programs and features' in the Start menu) and opened it up. Then, in the list of all the programs, I scrolled down towards the bottom where all the Bootcamp drivers are (meaning the Windows Driver Packages). I selected the Apple SD Card Reader driver (if you can't find it, just search 'Apple SD' in the search bar at the top right), and then clicked Uninstall/Change. Then I clicked Yes when the confirmation window appeared. Then I tried inserting an SD card into the reader, and it worked! It automatically installed a separate driver called 'Broadcom SD SCSI Disk Device.
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I hope this helps!