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GitHub User: DerekHill
I had the same error - "An unexpected error has occurred. We have been notified of the problem."
I got it working following the Stripe tutorial (https://stripe.com/docs/tutorials/forms) which uses https://js.stripe.com/v2/ and has some differences, including the 'data-stripe' attribute.
Tried to add drop-downs for the expiry date and was told by Stripe support "The data-stripe version of Stripe.js doesn't support dropdowns yet (we're working to fix this). In the meantime, feel free to copy the old method from https://gist.github.com/boucher/1750368)"