I am experiencing the same problem. I can see the Marlin attached in Windows 10 Device manager under Disk Drives and in Portable Devices. Windows 10 seems to recognize the Re=Arm board but not the SD card. I had it working with Smoothieware but decided to switch to Marlin to be consistent with my other printer. As soon as I switched to Marlin, the Re-arm SD drive is no longer recognized. I canby hmbfly - Firmware - Marlin