Same problem here. When the “Legacy Stripe Experience” is unchecked (so the new experience is used), this error pops out.
Activating the “Legacy Stripe Experience”, the error dissapears but a PHP Fatal Error appears:
PHP Fatal error: Uncaught ArgumentCountError: Too few arguments to function Wps_Subscriptions_Payment_Stripe_Main::wps_sfw_wc_stripe_force_save_source_callback(), 1 passed in /var/www/vhosts/XXXXXXXXXX.com/httpdocs/wp-includes/class-wp-hook.php on line 324 and exactly 2 expected in /var/www/vhosts/XXXXXXXXXX.com/httpdocs/wp-content/plugins/subscriptions-for-woocommerce/package/gateways/stripe/class-wps-subscriptions-payment-stripe-main.php:106
Temporary fixed by making the second argument ($customer) defaults to null.
