Facebook Pixel Help

Issue: Server External ID Not Matching to Pixel External ID for Purchase Event
You're sending the external_ID parameter for your Purchase event from your server, but you're not sending the external_ID parameter for this event from your pixel code. If you send external_ID for an event from your server, you should also send it from your pixel code for best results.
This may cause issues with the attribution and delivery optimization of your ad campaigns.
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Solution: Check source code
Send external_ID as part of your pixel init call. For details about the external_ID parameter, visit the Facebook for Developers site.