It is either you have a bad USB flash drive, or a bad USB port.
Since Genos has 3 USB slots, you can reboot Genos, and insert your current USB flash drive into any of the two remaining USB slots and try. If Genos still has problems reading your USB flash drive with both of its remaining USB ports, then your USB flash drive is at fault and have to be replaced by a good one.
If you have a known good USB flash drive that works on all other equipment like PC, Mac, or other keyboards, then your Genos might have a problem. Then you need to contact Yamaha customer support. This possibility is low though.
Thanks,
Paul