Get trouble in Return from Paypal

Hi S2Member !

Thank you for creating a nice and powerful plugin.
I’m developing a site on localhost and have an issue after checking out at paypal(sandbox).
After checking out, the paypal site didn’t redirect to the url which I place in the shortcode ( registration through paypalfor level 1 member ) :

[s2Member-Pro-PayPal-Form level=”1″ ccaps=”” desc=”$100 AUD + tax / One Time (for lifetime access, non-recurring, no trial)” ps=”paypal” lc=”AU” cc=”AUD” dg=”0″ ns=”1″ custom=”boca.demo” ta=”0″ tp=”0″ tt=”D” ra=”100″ rp=”1″ rt=”L” rr=”BN” rrt=”” rra=”2″ accept=”paypal” accept_via_paypal=”paypal” coupon=”” accept_coupons=”0″ default_country_code=”AU” captcha=”0″ success=”https://boca.demo/payment-is-completed”/%5D

but returned to the checkout pay before and showed the errors on the page ( with no UI – just text ) :

Notice: Undefined index: opt_in in /Applications/MAMP/htdocs/BOCA/wp-content/plugins/s2member-pro/includes/classes/gateways/paypal/paypal-checkout-in.inc.php on line 787

Notice: Undefined index: ws_plugin__s2member_registration_return_url in /Applications/MAMP/htdocs/BOCA/wp-content/plugins/s2member/includes/classes/registrations.inc.php on line 977

Warning: Cannot modify header information – headers already sent by (output started at /Applications/MAMP/htdocs/BOCA/wp-content/plugins/s2member-pro/includes/classes/gateways/paypal/paypal-checkout-in.inc.php:787) in /Applications/MAMP/htdocs/BOCA/wp-includes/pluggable.php on line 678

…

I’ve spent 2 days because of this so please help me this issue cause I dunno what i have to do now.

Thanks you so much.

https://www.ads-software.com/plugins/s2member/