A credit is used only if the read is produced.
If the report isn't generated, your balance does not change.
Why
You buy credits on the Credits page. A full report uses 3 credits only when a valid result is produced; a deep dive uses 1 credit.
How
If the pipeline fails or your read does not meet the technical conformity criteria (complete sections, minimum quality), credits stay available. No steps, no email, no refund to request.