[Fire HD 8 and HD 10 Original Android Development] anujdatar:
Hey, not sure what happened, but I turned my Douglas on after a few days and it was stuck in a boot loop or something. It got stuck on the LineageOS boot animation for a while and then rebooted to TWRP automatically. This happened every time.

1. I tried to clear cache, but it said

Failed to mount '/cache' (No such device)

2.

Then i tried re-flash the LineageOS ROM zip, that I already had on the internal storage and it said "Failed to mount (No such device)" for `/cache`, `/system` and `/data`.

Now I seem to have lost everything that was on the internal storage, and it cannot mount anything. It won't connect to my computer either. It says "No media storage found. Make sure device is unlocked and MTP is enabled." It seems like the data partition does not have any file system format. And am unable to create one either. It says

failed to mount and unable to recreate `/data/media`

I also tried the repair file system, but it gives me the same "Failed to mount" error.

I found an old TWRP backup that I successfully copied to the mounted SD card. But during restore using twrp, it says This /data backup was made with ext4, so i need to change it back to ext4 to ensure it boots. But it won't let me change file system using twrp

Formatting Data using mke2fs
Done.
Failed to mount '/data' (No such device)
Unable to recreate /data/media folder
Updating partition details...
Failed to mount '/system' (No such device)
Failed to mount '/cache' (No such device)
Failed to mount '/data' (No such device)
...done
Unable to mount storage

---

After talking with @Rortiz2 he said, I retried the entire unlock process all over again, but my tablet refuses to go into the Hacked Bootloader.

1. `sudo ./brick.sh` showed success

2. `sudo ./bootrom-step.sh` also seemed to work fine, it reached the last step and said Reboot.

3. But after this step, I get nothing when I do `sudo fastboot devices`. So I can't do `sudo ./fastboot.sh` to reload TWRP.

I can boot into the TWRP using the Volume and Power keys. From there I have ADB access, and I can boot into the regular Fastboot mode. But if I select reboot into "Hacked BL", it just reboots into TWRP.

If I boot into fastboot using ADB or TWRP, and try to write anything, I get an error saying cannot write on locked hw

sudo ./fastboot-step.sh
Your device will be reset to factory defaults...
Press Enter to Continue...

Sending 'recovery_x' (13196 KB) OKAY [ 0.471s]
Writing 'recovery_x' FAILED (remote: 'the command you input is restricted on locked hw')
fastboot: error: Command failed

Same error if I try to flash stock recovery.img

In TWRP, when I go to Wipe and select Advanced Wipe,

If I select System, or Cache, or data, I get the following

Mount Point: /cache, /data or /system
File system: <blank>
Present: Yes Removable: No
Size: 0MB Used: 0MB
Free: 0MB Backup Size: 0MB

And the only option I see is `Change File System`. I tried to format each partition to `EXT4`, but it keeps

Formatting data (or cahce or System) using mke2fs...
Done.
Updating partition details...
Failed to mount '/system' (No such device)
Failed to mount '/cache' (No such device)
Failed to mount '/data' (No such device)
...done
Unable to mount storage

PS: I am using Ubuntu 22.04, unlock tool v1.2, I have been using Rortiz2's LineageOS for a couple of years now. I was on the latest update of LineageOS 15.1, I believe it was the January update.

Thanks