Stripe Funding Instructions in Sandbox Environment

Based on the information provided, there are a couple of important points to clarify regarding your issue with funding instruments in a Stripe sandbox:

Issue Identification

1. The first error message indicates that an existing self-serve funding instrument was already found on your account, suggesting you can't create a new one because one already exists.

2. The second error (Internal Error) appears to be a system-level issue within Stripe's sandbox environment.

Important Limitation

According to Stripe's documentation, there's a key limitation that's likely causing your issue:

You can't test Issuing in a sandbox environment.

Funding Instructions are part of Stripe's Issuing service, which is used for topping up Issuing Balances via bank transfers. Since Issuing functionality cannot be tested in sandbox environments, this explains why you're encountering these errors.

Recommended Actions

1. For testing Issuing functionality, including funding instructions, you would need to use Stripe's standard test mode in your live account rather than a sandbox.

2. If you need to continue working with funding instructions, you should:

   • Use your live Stripe account in test mode
   • Use the test API keys (prefixed with sk_test_)
   • Follow the API documentation for creating funding instructions

API Example for Live Test Environment

When you're ready to test in the appropriate environment, here's how you would create funding instructions:

BASHCopied
curl https://api.stripe.com/v1/issuing/funding_instructions \
-u "sk_test_YourTestKey:" \
-d "bank_transfer[type]=eu_bank_transfer" \
-d "currency=eur" \
-d "funding_type=bank_transfer"

This should help you move forward with testing Stripe's Issuing functionality properly.