Hi Thomas,
I opened a similar issue some time ago, Boot failed: not a bootable disk / no bootable device after installing a Ubuntu image through ON .
Basically, I needed to select as 1st boot “HD’ and as second boot “CDROOM” in the template created to read from the cdrom and install in the new image. I am not sure if you are getting the same issues but I hope it helps 
Cheers,
Esteban