Post Purchase is not showing on my store despite setting it up.

Shopify has set some limitations regarding which orders are eligible for post purchase upsells.

You can read more here.

Here are the most likely reasons:

• Alternative payment methods were selected (such as Klarna, Affirm, AfterPay, Apple Pay, Amazon Pay, or Google Pay). You can check the supported payment methods here.
• Your store is multi-currency, and the order was made in a currency different from the store's default currency.
• The order was free ($0), or the customer used a Gift Card or COD as payment.
• The product’s inventory is tracked, and the inventory amount is equal to zero or less.
• Your product has been ordered for local delivery.
• Automatic billing is disabled on your store.
• The Shopify platform is overloaded.