I cannot add much more here to why it's not working.
I've added a PayPal Account earlier to test this, and no Age verification came to light.
I signed into my PSN Account with the mobile App, went to my Account details and to the Wallet and clicked PayPal. Entered my PayPal details (email and password) and then it took me to my PayPal web site (signed into PayPal) to confirm adding PayPal to SEN. Nowhere in any of the procedure did it ask to verify my age.
