Similar limitations will apply to the measurement of some web conversion events because of reporting limitations of iOS 14 devices. The following limitations are expected across Ads Manager, Ads Reporting, and the Ads Insights API.

Delayed reporting: Real-time reporting will not be supported, and data may be delayed up to 3 days.

Please refer the documents here to check further:

As a result, we suggest you to check the events on the past days instead of today (e.g Yesterder, last 7 days ...)

Facebook has updated Recommended and Maximum Delay Times for Web and Offline Events
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