My guess would be that you werent in the correct folder/directory when you ran the script. Others didnt change it to executable. I run everything from a Terminal window as I am old and oldschool.
Some ppl also said they had to increase the pauses from 40 seconds to 80....
There werent really enough details in your post to decipher the reall issue. We can talk about it in the chatroom if you like, but its busy today with the Unlocked Bootloaders....
well just to give you the details, heres what i did:
1) opened terminal
2) changed directories by entering
cd (dragging folder to terminal)
3) typed commands from OP exactly. even copy/paste commands the second time
4) chose the proper command to run (ie; update to OTA kernel from AP fastboot)
terminal would just hang. waited for 2 minutes and nothing. and yes my phone was in fastboot mode.
not expecting you to give me a complete walkthrough atm, just wanted to give you a better idea as to what i did. maybe we can talk about it later or maybe tomrrow when the chatroom isnt so busy. thanks for giving me some ideas tho