iPad mini2 Failed to restore device

[charles1503]

[+] Waiting for a device in DFU Mode
[+] iPad Mini 2 (WiFi) is supported

=============== DEVICE INFO ===============

Model Name: iPad Mini 2 (WiFi)
Hardware Model: j85ap
ECID: 2255621595372
APNonce:aed00d5e99ec777f60296b2bec2771e7788734c0
SEPNonce:1adf205b5b54982406bf62729582ba937818143e
CPID: 8960
Pwned: No

=========================================
[+] iPSW selected at /Users/charles/Downloads/iPad_64bit_10.3.3_14G60_Restore.ipsw and being extracted to /Applications/LeetDown.app/Contents/Resources/LDResources/iPSW
[+] Extracting the iPSW please wait...
[+] Successfully extracted the iPSW
[+] Running checkm8 exploit
[+] Successfully exploited device!
[+] Patching bootchain
[+] Fetching iOS 10.3.3 OTA blob...
[+] Waiting for the device to connect
[+] Sending /dev/null
[+] Waiting for the device to connect
[+] Sending /Applications/LeetDown.app/Contents/Resources/LDResources/iPSW/Firmware/DFU/iBSS.iphone6.release.im4p
[+] Waiting for the device to connect
[+] Sending /Applications/LeetDown.app/Contents/Resources/LDResources/iPSW/Firmware/DFU/iBEC.iphone6.release.im4p
[+] Restoring...
[+] Failed to restore device
[+] Running checkm8 exploit
[+] Successfully exploited device!
[+] Patching bootchain
[+] Fetching iOS 10.3.3 OTA blob...
[+] Waiting for the device to connect
[+] Sending /dev/null
[+] Waiting for the device to connect
[+] Sending /Applications/LeetDown.app/Contents/Resources/LDResources/iPSW/Firmware/DFU/iBSS.iphone6.release.im4p
[+] Waiting for the device to connect
[+] Sending /Applications/LeetDown.app/Contents/Resources/LDResources/iPSW/Firmware/DFU/iBEC.iphone6.release.im4p
[+] Restoring...
[+] Failed to restore device

I've tried many times, but it's still the same. How can I solve this?