As delivered, the USB Mode setting of the Sansa SanDisk is set to “Auto Detect”. The Auto Detect USB Mode is not compatible with Ubuntu for some reason in that the disk images cannot be mounted. I have not tried this with other Linux distros to date.
For Ubuntu (and probably other Linux distros), simply set the USB Mode on the Sansa to either MTP or MSC - both work.
For MacOS Sierra, I used the short USB cable that came with the Sansa product to connect - no issues at all, even in Sansa “Auto Detect” mode. Since I am no longer running “El Capitan”, I couldn’t say whether it works or not. Can you upgrade to Sierra?
