[LeEco Le 2 Guides, News, & Discussion] tsongming:
What should I do? You need to read, the answers to your questions are here a million times over. Always do your homework first. Also thank someone who helps you. Otherwise they will not continue helping you.

FlashOne: Why are you using FlashOne? You are not bricked. Also FYI, if using FlashOne , you have to be in EDL mode. not fastboot.

Now here is probably good news, since you can enter fastboot then you are very likely just fine,and you are definitely not bricked. However, you will probably end up losing any files that you had on the phone, because the user data( storage ) will most likely need to be formatted, (type yes reboot to recovery)

So my instructions are to help get your phone working again, not to recover data. Unfortunately, you didn't provide much information so I have to assume some things.

Is the bootloader unlocked?

Have you flashed custom roms before?

Which phone do you have? A Leeco X5?? A Leeco X6??

Let guess and say that maybe bootloader is unlocked, you are asking a question on XDA so maybe that is a safe guess?

What you need to do is use ADB or the the Tool all in One and flash Recovery and root. Here comes the reading part again, I can't explain everything or I will be here all day. I assume that you know how what Recovery and root is?

Download the correct TWRP Recovery for your device, if you don't know your way around ADB too well.

You can use Mauronofrio's "TOOL ALL IN ONE" for removing encryption, installing TWRP, Root, your ROM, Gapps, and even to restore to stock Recovery, or to flash a stock Rom

Read that thread for instructions or for any questions.

If your device not recognized it is a usb driver issue, ensure that device drivers are installed and You will need to reinstall the Google USB driver, and while you are at it check to make sure adb is up to date. The All in One tool can do all of this for you, its with the advanced menu section. ** You will need to temporarily disable Windows defender for installation. **

Use the All in One tool to flash Recovery, then boot to recovery.

Ensure that you have TWRP installed permanently by rebooting to Recovery and then rooting the phone.

Always reboot to Recovery and check the boxes to install TWRP when rebooting to recovery

To remove encryption you will always need to format the storage

Not wipe >> Choose Format > type yes> Reboot to Recovery)**

(If you see a message that says there is no OS installed are you sure> Click Yes, then reboot to Recovery, ignore message about no OS)

When you reboot to recovery swipe to be able to read and write to the device.

Use an OTG Usb adapter to connect a USB to your phone and flash your prefered rom, Gapps, and root. Reboot to recovery, thenn reboot to system. If you were successful, the error message will be gone and you will be able to set up the phone.

As mentioned the tool will help you with installing your rom, Gapps, and root.

The All in One Tool can completely restore your phone to stock if absolutely needed. It actually links to Mauronofrio's server and it has all of the significant EUI Stock Roms, in case you want to restore the stock rom.

Hopefully this helps you, Good luck.