Computer does not recognise new M250

Hi - I’ve just plugged in my brand new m250 and its not showing up on the computer (as ‘removeable disk’ or anything else) - as a result I’ve nowhere to drag my music to!  Instructions simply say to plug it in (i’ve tried a couple of ports) and away you go!  Any advice please?

Many thanks!

Replying to my own message here but in case anyone needs to know in the future - I changed USB mode from auto detect to MSC and now its working fine.  The simple instructions which come with the machine aren’t detailed enough to know about doing this - used this website to work it out - think SanDisk could do a better job at informing new purchasers of such detail.