No response (time out?) after at step 6 booting from APX to fastboot

[Smurfjet]

Steps 1 to 5 working properly from what I can tell, they executed as per instructions, however after executing step 6

smurfjet@ubuntu:~/tegra30_debrick$ sudo ./utils/nvflash_v1.13.87205_miniloader_patched --setbct --bct ./bct/nexus_7_grouper_bct.bin --configfile ./utils/flash.cfg --bl ./bootloader/bootloader-grouper-4.23.img --go Nvflash v1.13.87205 started

The command appears to hang, and after 45 minutes I had to force close the terminal. Any ideas what might cause this behaviour? P.S. I'm a beginner. Thanks!