my rekordbox doesnt recognize USBs to export

It was working perfectly with the same usbs before and suddenly it stopped working

- yes the USB is FAT format (it worked with it for many years' RX2 reads it perfectly so it is not a formating issue)

- yes I am in export mode

- it shows under explorer in rekordbox but not under devices

- re installed latest rekordbox 5.8.7, still the same

what else can I do? please help