If you are formatting, or reformatting an SD card, Uniden states the following on page 52 in the manual.
"SD cards should only be formatted using the special SD Card Formatter (
home - SD Association downloads/formatter_4/). Then, you need to “Clear User Data” using Sentinel to restore all files and directories to the card. After formatting, the scanner won’t be automatically detected (since it is wiped clean), so you may need to uncheck “Hide empty drives” in Windows Tools>Folder Options>View before doing the “Clear User Data” step."