Amazon Launch Template - Updated AMI

Ok after a few tries I've discovered that the hint is in the error message as unclear as it was at the time. What I didn't do when creating the new version of the Launch Template was, after updating the AMI ID, I also needed to update the Snapshot ID of the volume used by the template, to the Snapshot ID of the snapshot created when the AMI was created.

Would help if when changing the AMI, it searched a list of existing AMIs then allowed you to select the one you want which will then update the template with the necessary things such as Snapshot ID...

c'est la vie