When I use the Step in a Process for one of my projects, I am correctly prompted to choose a variable from my Project of type AWS Account.
When the deployment of that project runs, the first line of output gives me the name of the AWS Account that is passed as a parameter, as I expect. However $aAWSAccount.AccessKey is null.
Is there a difference between how AWS Account variables are accessible in a regular step as opposed to as a parameter in a Step Template?
Coincidentally, I found the same the other day and ended up fixing it while I was looking at something else. Keep an eye on this issue - it should be released in the next few days.