1, What does a read stage return to you - does it return True and False for that radio button?
2, If not - experiment with the other attributes for your element. Do any of your other attributes indicate the value of the radio button to you - if so you can use a read stage to get the attribute value.
3, If nothing else works you can use image recognition (Surface Automation training) to recognize if the selected radio button image exists or if instead the not selected radio button image exists.
This kind of experimentation and moving onto a different technique if the one does not work is the bread and butter of an RPA developer.