On the root of your SD card (not inside apps ), create a folder named (all lowercase). This is where you will place your .wad files – games, channels, or IOS WADs.
It supports various storage devices, including the internal SD slot (with SDHC support), USB 1.1 and 2.0 devices, and SDGecko.
: Compatible with internal SD slots, SDGecko, and USB 1.1/2.0 devices.
This occurs when the WAD file tries to write to a protected area, or the selected IOS does not have the necessary custom patches enabled.