Hello jeanpaul1,
Thanks for reaching out to us.
I have reviewed your query that, you are unable to switch radio button to drop down.
I have reviewed in our latest version and I can see it is working fine.
Click here to review it.
So, it might be possible that another plugin or current activated theme conflict with our plugin and it does not working.
Can you please provide the list of activated plugins and current activated theme name so, we can review it at your side and get back to you.
Please also check that if your theme contains the below file then it might conflict with our plugin file.
Path: themename/woocommerce/cart/cart-shipping.php
If above file exists then, rename it to bkp_cart-shipping.php
and let us know it works or not.
Note: Please take the backup of the file if you try to remove it.
Let us know still you need any further assistance.
Thanks,