I figured I'd **** around with it again while waiting for guidance on how to make unlocking the bootloader on my Sprint V405UA work. And I got it to work! Amazing!
Here are some additional pieces of advice on how I got to be successful:
1) I had all of the files I needed to upload/flash in a folder right off of C: drive. No long convoluted paths. Just straight C:/v40root.
2) Load up QFIL first. Have that program up and in the foreground as you try to get into 9008 mode.
3)
@argon9898 His advice on how to get into 9008 mode was invaluable: The key to activating EDL mode is to hold all three buttons down: POWER + VOL UP + VOL DOWN while the phone is still on. After 8-10 seconds the screen will turn off. When the screen turns off keep holding POWER + VOL DOWN while REPEATEDLY PRESS VOL UP. That should get you into EDL mode.
4) As you successfully enter into 9008 mode, the top line of the QFIL program will switch from
No Port Available to
Qualcomm HS-USB QDLoader 9008 (COMX). That is your definitive clue that the phone is ready for the v35 Engineering bootloader.
5) Load the v35 Engineering bootloader as described. DO NOT EXIT out of any of the QFIL screens. Leave them up as is.
6) Perform the exit out of the 9008 mode into v35 Engineering bootloader mode as described. The bootloader will look strange. Different color text by lines, and the volume button will cycle through Restart, Power Off, then some Fastboot gibberish. If that's what you see, you've loaded the v35 Engineering bootloader successfully.
7) Perform the fastboot commands as described.
8) Once done with the fastboot commands as described, unplug the USB-C cable from the phone.
9) Use the volume keys on the phone select Restart (or something along those lines, I can't remember now).
10) The phone will flash a warning about bootloader unlocked, then begin its normal boot process. That boot process will take a bit longer than usual because userdata was wiped unlocking the bootloader.
Good luck!
[NG]Owner