: In uLaunchELF, try entering the empty mass: folder, then backing out, unplugging the drive, replugging it, and entering again. This can sometimes trigger the driver to remount the device.
If your drive is formatted as or exFAT , uLaunchELF will not be able to read it.
If you follow these steps, you should be able to resolve the "uLaunchELF mass empty" error and begin running your homebrew applications. If you are still having issues, consider: ulaunchelf mass empty
If your USB drive is larger than 32GB, download a third-party tool like GUIFormat (FAT32 Format) to force-format the drive to FAT32.
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If you are trying to use an external USB Hard Drive (HDD) or a power-hungry USB 3.0 stick, the PS2 may not supply enough power to boot the drive's controller. Plugging your drive into a wall-powered USB hub, and then plugging that hub into the PS2, frequently resolves the issue. Step 4: Upgrade to wLaunchELF
UlaunchELF Mass Empty: Techniques, Risks, and Best Practices : In uLaunchELF, try entering the empty mass:
Some modern USB 3.0/3.1 flash drives draw too much power or use controllers that the PS2's USB 1.1 ports simply cannot communicate with.