I flashed a card with the OctoPi 0.17 image using balena etcher.
I have tested this Pi and SD card combination and it runs standard raspbian with no problems.
I updated the bootloader using the official method and had no problems.
I guess that's why you can't boot an "older" image.
Do you own another pi? You could boot the image with the other pi and run sudo apt update && sudo apt -y upgrade
Ah thanks so much, the nightly works! I guess my pi must have come with an already too updated bootloader? I tried it straight out of the box with and it didn't boot either.
Seems that webcam support is not working on the nightly, so I guess my options are to install octoprint myself or wait?
My bad, still new to raspberry pi and I didn't realise you need to have the usb webcam attached while booting. I tested 32 and 64 bit, my webcam only works with 32 bit.
Think I'm ready to actually print now. Thanks again - really appreciate people like you who make it possible for us newcomers to get going.