Post-purchase offers can only be shown when the payment method allows a silent follow-up charge on the same order. When your customer accepts an upsell, they are charged automatically without re-entering payment details, and not every payment method supports that. This is a Shopify platform rule that applies to every post-purchase app, not just Post Purchase Upsell Hero.
Only a part of your orders is eligible for an offer. If 40% of your customers pay with Klarna or wallets, your impressions will always be well below your total order count. That is expected and the same for every post-purchase app. See Analytics explained for how to read your display rate.
If an upsell was skipped on a specific order, the payment method is the most common reason. See Why wasn't my upsell displayed? for the full checklist.
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