In the spirit of providing solutions rather than just listing problems:
I finally found a microHDMI adapter so I could see what the problem was when the navio SD image booted up. The boot hung when trying to load the “start4x.elf” file - with the system stating it was incompatible and should be updated. So I took another SD card with the latest release standard raspberry pi image, boot up the board with that, ran updates, then shut it down. Then I copied the start4x.elf file from that SD card onto the EMLID imaged SD card, then tried again.
Worked like a charm - problem solved 