Fred28 What steps are you taking to burn the iso file in the disk? Can you mount the iso and test to make sure it works, then load the iso into EX Burn again and try again but make sure to use a slower writing speed. You might also want to contact NCH Tech support for help: https://www.nch.com.au/support/index.html 
Bamink If you burn iso, it’s best to use a burning tool, which will burn the iso directly to the disk.