Hi. Doesn't sound like you're doing anything wrong unfortunately. When i use etcher to write an image, e.g. mobian-pinephone-phosh-20201229.img.gz or pine64-pinephone.img.xz, to my SD card, then when I put my SD card into the phone, it will always boot from it. Assuming you've put your SD card the right way round into the upper slot, which I'm sure you have, then there doesn't sound like there's much else you can try. I suppose you could give the contacts on the card a bit of wipe and maybe blow into the slot on the phone? But unless anyone else can suggest anything, it sounds like you may have a hardware problem.
EDIT: I suppose yu could do some reading up on SD card compatibility, e.g. https://forum.pine64.org/showthread.php?...&pid=78509 just in case you're very unlucky and have 2 incompatible ones?
EDIT2: I suppose the fact that it does something different when the SD is inserted is a good sign. Is your PP 2GB or 3GB as I think there were some issues on 3GB models with older images, but Jumprive 0.6 onwards should work as should the latest version of most OSs. Hope someone can come u with some ideas for you.
EDIT: I suppose yu could do some reading up on SD card compatibility, e.g. https://forum.pine64.org/showthread.php?...&pid=78509 just in case you're very unlucky and have 2 incompatible ones?
EDIT2: I suppose the fact that it does something different when the SD is inserted is a good sign. Is your PP 2GB or 3GB as I think there were some issues on 3GB models with older images, but Jumprive 0.6 onwards should work as should the latest version of most OSs. Hope someone can come u with some ideas for you.