Don't treat every failed card payment as the same decline. Start with the decline reason or issuer response before deciding what to change or whether to retry.
A practical diagnostic checklist, worked through in whichever order the available data allows:
Decline reason/code - card status and balance - card controls - merchant/MCC/GEO · 3DS result - BIN/card product - infrastructure errorRecord, for each declined authorization: decline reason or response code,
BIN, card product, merchant, MCC, merchant country, transaction currency, transaction amount, 3DS result, transaction type, card status, the limits and controls in effect, and retry history.
Then segment the decline rate instead of reading it as one account-wide figure. A single BIN may produce a disproportionate share of declines at a specific merchant type. One MCC may be blocked by a configured card rule. One geography may show more failed authorizations than the rest of the portfolio. 3DS failures may account for a large share of declines. Repeated retries may inflate the gross decline rate without changing the actual outcome. None of this shows up in an aggregate percentage.