[Miscellaneous Android Development] martyfender:
Sounds like either adb and or fastboot is not working correctly.

USB debugging must be enabled in developer options.

bootloader must be unlocked. if you can't get fastboot working, you will not even be able to enter the fastboot command:

flashing unlock

which unlocks the bootloader.

I recommend opening a command prompt in the folder where adb and fastboot are installed and beforehand have twrp and boot.img copied to that same folder. Shift, right click: open a command prompt here.

If adb and fastboot are not truely installed system wide the above method is recommended.

I always do it this way on Windows. In Linux I only have to right click in the folder where I have twrp and my boot.img installed and choose "open in terminal" because in Linux it is system wide by default.

Make sure you have the latest adb and fastboot binaries and the Intel adb and fastboot drivers

If you are on Windows 10 it is much more complicated to get unsigned drivers to install properly.

With the tablet booted and connected with a computer normally type:

adb devices

here is my output from Linux Mint:

mint@mint ~ $ adb devices
List of devices attached
YFGV0317037600	device

your device should be listed above if adb is installed correctly and you are running the command from the adb folder.

with the tablet off plugged into the computer:

hold the volume down and power button at the same time

to boot into bootloader or fastboot mode. you should see the litte green android guy on a black background with white red and green text.

at the bottom you should see:

SECURE BOOT - DISABLED
LOCK STATE - unlocked

if you unlocked your bootloader beforehand.

type;

fastboot devices

you should see your device listed similar to mine on Linux:

mint@mint ~ $ adb reboot bootloader
mint@mint ~ $ fastboot devices
CHTT011AC12A	fastboot
mint@mint ~ $

Note the adb command I used to go straight to bootloader mode without shutting down and using the key combos. the key combos were given as a less fullproof way to get to bootloader mode.

Since you are in Windows it will be slightly different, but not much.

to summarize:

1. the proper windows adb and fastboot drivers showing up in the Windows device manager

2. bootloader unlocked

3. USB debugging enabled

4. adb and fastboot binarys installed

5. twrp and boot.img copied to the Windows adb folder

6. supersu.zip, busybox.zip and root checker copied to the internal or external SD

7. entering the commands properly: the proper syntax and spaces, etc.

You can also create a shortcut for the Windows command prompt in this folder and right click, and choose "run as administrator" before you enter adb and fastboot commands, as a confirmation you are truely running as an administrator.

Update: I installed Intel adb drivers and simple adb on an older Windows 7 laptop to test for potential problems and did encounter isssues.

With the tablet booted normally and plugged in I saw In the Windows device manager:

Intel adb interface, which is correct.

When I rebooted the tablet in bootloader mode I still saw: Intel adb interface in the device manager.

I double clicked that and then chose the driver tab.

I then chose the update driver button, browse my computer for driver software. Then: let me pick a list of device drivers on my computer.

Uncheck: show compatible hardware. Choose Intel Android Bootloader interface. click next, you will get a message: Installing this device driver is not recommended. . . . . . . . . . . . , click yes to install it.

confirm it was successful.

now from the command prompt, the tablet booted into fastboot mode type:

fastboot devices

hit enter

Here is the output show my device is connected:

C:\Windows/system32>fastboot devices
CHTTB91032BE fastboot

fastboot boot recovery twrp Ares8A_recovery_twrp.img

to temp boot twrp and you should be good to go from here to do your backup of the system before following the later steps.

One thing I forgot to mention earlier, you will get a security prompt in your tablet screen which you have to approve and check the always box or you will not be able to get the adb or fastboot commands to work.