Hey purefox,
Thanks for using Apple Support Communities! I understand you accidentally sent a gift card to an incorrect email address. I definitely want to make sure you're able to access your gift card, and I'm happy to get you pointed in the right direction.
To start, I want to share the resource below with you. It sounds like you're already well aware of how to resend a gift, so this just ensures you're not missing any steps. Also, if available, I recommend attempting to resend using a different device as well.
Send a gift from the App Store, iTunes Store, Apple Books and more
If you're still unable to resend that, reach out for additional assistance here: Contact Apple Support
Thanks again, and have a great day!