I actually ran into something similar. Although the image was updated to include the new Raspberry Pi 4, they’ve seemingly had new revisions of the board. I had to take the SD card and put it in a RPi3, so a sudo apt-get update
and then sudo apt-get upgrade
to get the newer kernel and firmware. Once that was completed, I put it back in my new RPi4 and it worked fine.
I’ think the 260mb being seen from the imaging was likely just the FAT32 /boot that would be seen by Windows. From the later post it does show there were other partitions (but Windows doesn’t know how to read them.
If you cut out the other stuff from that post:
Windows can’t (without effort) show the contents of that 2nd partition.
My theory is the image is fine and being written correctly, but the current image can’t handle recently made RPi4. This isn’t a terribly uncommon problem with the RPi’s. They get minor updates/tweaks and require updated firmware to be usable.