Failed to load Android and TWRP recovery after flashing twrp recovery image The device is Lenovo Tab 2 A8-50LC
I flashed the device with a (apparently) TWRP recovery image.

./fastboot flash  recovery recovery.img 
target reported max download size of 134217728 bytes
sending 'recovery' (10454 KB)...
OKAY [  0.904s]
writing 'recovery'...

OKAY [  0.306s]
finished. total time: 1.209s


After that:

./fastboot reboot
rebooting...

finished. total time: 0.052s


But the device can not load TWRP or Android and restarts consequently.
No power-off, volume-up or down or any combinations work here. Nothing works:

./adb reboot recovery
error: no devices found

./fastboot devices

./adb reboot bootloader
error: no devices found


The only way is to disconnect the battery from the board.
Any suggestions highly appreciated.
I tried adb reboot recovery at the earliest time I see Team Win is starting up. That works and give me the fastboot mode.
Then I flashed another recovery image.