When you say there is no pin assigned, we mean that you need to clear the pin that is assigned aileron under SETUP MENU > EMS SETUP > SENSOR INPUT MAPPING. The pin in question will have POSITION in both the "function" and "sensor" columns, and AILERN in the "name" column. Note that you may need to scroll down the page (you can only see the first 14 pins, and it goes to 37).
Alternatively, do you have a VP-X by chance? That changes things somewhat.