If I had to guess you have restored the avatar / Kinect data with a newer system update than what the Jtag / RGH 360 was on, doing this will brick the console.
Without Xell the only way to recover is to solder a nand flasher to the 360's motherboard and restore a backup of the nand from before you updated.
Something was probably selected incorrectly when building your new hacked nand update if I had to guess. As to what exactly its impossible to say as I don't know how your Xbox 360 was hacked (Jtag, RGH, RGH2 and so on) or what options you chose when building the new hacked nand.
Do you have a backup of the Xbox 360's nand from before you updated? if so you can use a usb nand flasher such as the Nand-X for example to flash this working nand back to the 360. It should then work the same as before you attempted to build a new nand.
The nand is the Xbox 360's onboard storage, essentially where it it stores the operating system & unique identifying info is stored which allows the Xbox 360 to function.
You need something like the nand-x to flash an update to the nand over USB from a PC: https://www.ebay.co.uk/itm/174319105441 - (you will need to solder this to the 360's motherboard)
Have a read here for info and how to set it up: https://consolemods.org/wiki/Xbox_360:Standard_NAND
Essentially the end result will be you can read and write to the 360s nand over USB from a PC.
What backups do you have?
Do you have the consoles original nand from before it was hacked?
Do you make a backup of the existing hacked nand before following the YouTube video to update?
The CPU key is unique to each Xbox 360 console, so your key will be different to any videos you see on YouTube.
The 1BL key is the same on all 360's, so you might be confusing the CPU key with that.
I suspect you probably have the original RGH hack given you have a x360run.
Either way you need some way of writing to the Xbox 360's nand, if you can get that ability with a Pi Pico, Nand-X or any other way then you are in a good position to hopefully fix the Xbox 360.
Please be aware I have Jtagged one Xbox 360 13 years ago for my personal use, so I can only be so much help to you with this. However if you can read / write to the nand from a PC then you can build a new nand and flash that to the console, hopefully fixing it.