Hello, @Fiano
Thanks for tagging us here.
Please note that the configuration of the Stripe payment system should be finished by yourself (keys or APIs). That’s why it is not set in your application 
As it was mentioned in the first message of the thread, The standard Stripe from Bubble does not have the action for refund.
Please check the screenshots, provided earlier in this thread (the space between the Bearer and sk is required):
Also, please allow to recommend you to check the documentation for the Bubble Stripe plugin:
https://docs.zeroqode.com/other/connecting-stripe-payment-using-stripe-plugin
Also, please find this official documentation for the Refunding and Canceling payments in Stripe:
Please check this first and let us know about the result.
Best regards,
Zeroqode Support team