You got the error that says " All domains need to be associated with a pixel event pair and an ad. Your pixel event was not associated with any domains".

Ads without domains will be paused unless you either set up your domain in Events Manager, select another pixel event or change your optimization.

This is something all advertisers need to do on Facebook due to the iOS 14 update. You need to go to business settings - brand safety and verify your domain. Then go to events and add events to the domain. Facebook has a guide here:

Go to Events Manager.

Click the pixel you want to use.

Under Aggregated Event Measurement, select Configure Web event.

Find the domain you want to configure events for.

Click Manage Events -> Edit

Select your pixel or custom conversion under Pixel / Custom Conversion.

Choose the event you want to configure under Event Name.

Verify domain and Configure and prioritize events are steps from Aggregated Event Measurement protocol, please find more information in here.
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