Missing AddToCart User Data Parameters

Hello,

I keep getting the below error in Pixel Diagnostics on Facebook but the Inspector shows that the User Parameters are being sent upon adding to cart.
Please advise. Thank you.

Missing AddToCart User Data Parameters
Your server isn’t sending any of the necessary user_data parameter keys for your AddToCart events. Without at least one of the below user_data parameter key for each AddToCart event sent from your server, you won’t be able to use your AddToCart events for attribution or optimization.
This may cause issues with the attribution and delivery optimization of your ad campaigns.

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