root was success . using Magisk and QFIL. then tab is open and run perfectly.
after that i restarted then it stuck on fastboot .

1. then i tried to fastboot erase userdata
but show error FAILED (remote: device is locked. Cannot erase)
2. then try to open tab using vol+ , vol - and power to open
it open and then wipe system but not worked, then try to adb mode
3. and use command adb reboot edl but it show error: closed.
4. cannot goto download mode again.

can any one help me with this. if i able to run adb reboot edl then i can put stock rom again.

Thanks.