Deduplication Key for Pixel

[ReadytoWear]

Hello everyone, 

My name is Eric. My business partners and I just started using Shopify this year, and as far as setups goes it was pretty straight forward, so even though we didn't have any IT guys on our team, we still managed to set it up. 

However, just a week ago, there was an error message appeared on our Facebook Pixel panel saying some of our ViewContent events don't have a deduplication key, so they're unable to cross-check whether they're duplicate events. They asked us to add "deduplication keys" to ViewContent events received by both your pixel and the Conversions API.

Has anyone encountered similar situations or anyone who can helped on this?

Thanks for your time and greatly appreciated if can help us out.