What Can a Lack of Verification Result In?
Verifying your custom events in the Meta Event Manager is a necessary step – if you skip it, you will not be able to use these events in ads, custom conversions or custom audiences.
Source: Facebook Ads Panel
How Do I Check if I Need to Verify Custom Events?
To check if you need to verify custom events, go to the Events Manager in Meta Business Manager. Then select the ‘Data Source’ section and select a specific Pixel. You will find a blue ‘Verify’ button in the events marked with a warning.