Cannot flash beagle bone black

Hi
I have an old BBB that used to run a lasersaur, it still has the ubuntu /lasersaur software on it. I want to flash it with the latest debian, I have tried o many times it i ridiculous.
I have used both dd and etcher to copy the image onto the disk, I have edited the text file on the boot directory. What else can I try.
Please help
Thanks

Well, let's see your serial boot log to see what's really going on..

Regards,

On Wed, 13 Feb 2019 10:43:17 -0800 (PST),
aaron@cnccraft.co.uk declaimed the following:

I have an old BBB that used to run a lasersaur, it still has the ubuntu

edited the text file on the boot directory. What else can I try.

  If it is really old -- you may need to hold down the [boot select]
button to get it to boot from the SD card... You may also be encountering
an old u-Boot that expects the kernel to load the device tree while new
systems expect u-Boot to have loaded the device tree.