I might have messed up here...
Got a new OnePlus 6T in the mail today. It has Android 9 on it. I enabled developer mode and USB debugging. The UBports installer (on a Ubuntu host) picked up my device and restarted it into fastboot(?). It asked me to unlocked the phone and I agreed, but failed.
I can't select/copy/paste, but the relevant parts are: cmd: fastboot oem unlock
and Flashing Unlock is not allowed
I searched a bit how to get into fastboot myself. Restarted the phone and booted into Android without issues. I Installed locally android-tools-adb android-tools-fastboot
and adb devices
listed the phone.
Then shut it down to try the vol up + vol down + power button combination, but it doesn't respond to that. In fact, it doesn't respond to any button presses at all anymore. Not the normal power button, no combintion, nothing. Just a permanent black screen.
What might have gone wrong, or better, how can I recover from this?