Issue with Accept Task smart service

I'm not sure I understand the entire sequence of your model here or what you are trying to do, but I recommend trying to get "Accept Task" working once, and then seeing how it works in your loop. Upon running the Accept Task smart service (and passing in the correct ID), the task should be Accepted by the user whose context is running the Smart Service.
If the task can't be accepted by the given user, it will return an errorOccurred and errorTxt parameter. Did you verify that the outputs of the service indicate success? And that you are passing in the correct Task ID? Since you are running it in a loop, each time the task is initiated, it will get a new ID.

I'm not sure I understand the entire sequence of your model here or what you are trying to do, but I recommend trying to get "Accept Task" working once, and then seeing how it works in your loop. Upon running the Accept Task smart service (and passing in the correct ID), the task should be Accepted by the user whose context is running the Smart Service.
If the task can't be accepted by the given user, it will return an errorOccurred and errorTxt parameter. Did you verify that the outputs of the service indicate success? And that you are passing in the correct Task ID? Since you are running it in a loop, each time the task is initiated, it will get a new ID.