One common reason for this issue is that your Paid Applications Agreement in App Store Connect is not in an Active status. If your agreement is pending or expired, IAP will not initialize, and you'll get errors like IAP not initialized.
Make sure to check the Agreements, Tax, and Banking section in App Store Connect and ensure that your Paid Applications Agreement is active.
Regardless of the plugin you're using, you can find more details on troubleshooting this issue in the Essential Kit plugin documentation here:
🔗 [Essential Kit - Billing Services FAQ] - https://assetstore.essentialkit.voxelbusters.com/features/billing-services/faq#why-initializestore-call-returns-empty-product-list-in-the-callback
Let me know if you need further assistance!
Thanks,
Ayyappa