Default [Q] Cannot boot G Pad 8.3

I have rooted my device following

Today the device asked me to update something (from LG), and I pressed it brainlessly.....and it crashed the OS

It then booted into the TWRP. Again, I wiped the system......

Now, the pad has no OS, and cannot be booted into TWRP or anything.

It keeps on show me the LG Logo and
Secure booting Error!
Cause: Device Unlock! So boot success!!
Can anyone help? Any little suggestion will be appreciated