Credentials
After reinstalling, return to USB Loader GX, set "Game's IOS" to 249, and the error will vanish.
Before troubleshooting, understand the error. When USB Loader GX launches, it sends a signal to the Wii’s USB ports (specifically Port 0, the bottom port on older Wiis, or the outer port on newer family editions). The loader expects to find a compatible USB storage device formatted correctly (WBFS, FAT32, or NTFS).