Have you downloaded/installed the latest firewire driver for Windows 10 (if available)?
Iām not 100% certain but this might be it.
https://usa.yamaha.com/support/updates/tools_for_n_win64bit_latest.html
It is possible that the N8 is too old to work with Win 10. I had a similar issue with my PreSonus Firebox audio interface. I could not get it to work with Win 10 so I had to purchase a new interface.
Regards 