This is just a quick note for anyone facing this issue.
A few of us lost about a day debugging what we thought was a terraform issue originally. While we were creating an auto scaling group (ASG), we were getting “Invalid details specified: You are not authorized to use launch template…”.
It turned out that the same error was presented in the AWS console when we tried to create the ASG there.
After some substantial debugging, it turned out that terraform was allowed to create a launch template with an AMI (Amazon Machine Image) that did not exist. We had used the AMI ID from our non-prod account in our prod account, but AMIs must exist in each account with unique IDs – so it wasn’t working.
It took us a while to get to this point in our debugging because, frankly, we were very astounded that the error message was so miss-leading. We spent a very long time trying to figure out everything that could trigger a permissions error on the template itself, not realizing that a missing resource used within the template would make the whole template present that error.