Question TWRP: "E:failed to mount /sdcard (Invalid argument)"

I formatted my Kindle Fire using my Mac computer as a Mac OS Extended (Journaled) drive. Unfortunately, when I tried installing a ROM on my Kindle, it did not succeed. So, I wiped the cache, Dalvik cache, and system (oops), and performed a factory reset. However, when I attempted to wipe the external storage, it Failed. The error message stated:
Code:
E:failed to mount /sdcard (Invalid Argument)
E:tw_format_rmfr: failed to mount "/sdcard"
 * Verifying filesystems...
 * Verifying partition sizes...
E:Unable to mount '/sdcard' (tw_mount)
E:Unable to mount '/sdcard' (tw_mount)
E:failed to mount /sdcard (Invalid Argument)
E:failed to mount /sdcard (Invalid Argument)
E:failed to mount /sdcard (Invalid Argument)
Additionally, the Kindle Fire has no OS installed (since I wiped to system), and the ADB shell does not recognize my device. Any ideas on what to do? Thanks to anyone who responds!