If you don't see any installs and events from Apple Search Ads in your AppsFlyer Account, it means you haven't set up the tracking.
Remember that SearchAdsHQ receives information from MMPs. This way, if there's no information to pass, we can't receive it.
So, always make sure you have set up AppsFlyer to receive installs and events before integrating it with SearchAdsHQ.
Here's how to set it up in AppsFlyer https://support.appsflyer.com/hc/en-us/articles/213747963-Apple-Search-Ads-Configuration#Setup.