How are you flashing the vbmeta? And where are you getting it from? I flashed with this:Hello! I need a bit of help... I have a TB-606F, 4GB/64GB version
I'm stuck on step 5. I've unlocked the bootloader, flashing TWRP and vbmeta seems successful, but then I cannot reboot into recovery. Using the fastboot reboot command I get "fastboot: usage: unknown reboot target recovery". If I try to reboot using volume up + volume down + power it eventually boots to Android.
Any thoughts are much appreciated!
fastboot --disable-verification flash vbmeta vbmeta.img
then rebooted to recovery:
fastboot reboot recovery
It seems to take forever once you're in recovery to actually boot TWRP, so just keep pressing the power button until you see something. There's also the key combination (which I honestly can't remember right now) which should 100% drop you into recovery.