@mattux

I tried this out again and this is the best way to get to Fastboot for me.

@mmvanheusden

OK. From a blank screen (Off) try only holding the volume up and then the power button as well until something happens.

Also have you left the phone plugged in as the OnePlus One can misbehave on very low charge.

Hi

I had similar issues with the OnePlus One.

I think your log is indicating that USB debugging was not set up:

"device unauthorized.\nThis adb server's $ADB_VENDOR_KEYS is not set"

This is a bit tricky to get around as it means only Fastboot can be used so you'll need to get into that mode.

In this respect I found that the phone buttons keys had to be held for some time before anything happened per these instructions:

https://www.androidexplained.com/boot-oneplus-one-fastboot-mode/.

If you can get to Fastboot, to get the phone back to stock and then have another go at setting up USB debugging follow this guide which only uses Fastboot commands:

https://forum.xda-developers.com/oneplus-one/general/guide-return-opo-to-100-stock-t2826541

Mine is now all working - this may work for you