AW: It can happen that the file system of the data carrier is corrupt or damaged, or that the formatting of a data carrier is lost due to several aborted read/write cycles. The causes for this can be of various kinds, such as the specific use or storage of the data carrier, as well as problems with the initial formatting.

In such cases, you must format the data carrier again, using your PC or notebook and the FAT32 option. Data carriers which are still not recognized by the device after new formatting indicate some sort of incompatibility of the data carrier controller chip. Then, you should try use a different USB stick from another brand.