Can't see usb stick with file manager

When I insert a usb stick in my aquaris m10, file manager shows nothing. The external drive app shows that the stick is there, as well as the sd card, but file manager only shows the sd card. I have tried inserting the usb before turning on the tablet, but that did not work.I have tried with the file manager locked and unlocked, showing hidden files... nothing seems to work. Hope you can help me.