When checking “Evaluate All Rows”, no value can be returned from the Decision Table. This is because all rows will be checked, and for each, their actions are performed when their condition is satisfied. So properties can be set, but no return value is allowed.
I'm calling it from a strategy. As explained in the I'm not trying to return multiple values, but i'm trying to append to a list for each row in the decision table. The output of the decision table is irrelevant.
I was able to fix, and currently working with the setup I was asking.