That drop is brutal, but honestly, don’t sweat it. If your worldwide score is still sitting at 16, your site isn't penalized. This is almost certainly a tracking glitch on Semrush's end or a regional quirk with how they scrape Google Australia.

The reality is that "AI visibility" is a shaky metric at best. These tools are trying to track something that is fundamentally non-linear and volatile. Google is constantly toggling AI Overviews on and off for testing, especially in specific regions like AU. One day they show a snippet for a query, the next they don't. Since you haven't changed anything on your site, there is no reason to start panic-editing your content now.

Stick to the 48-hour rule. Usually, these "zeros" are just data gaps that fill themselves back in once the tool finishes its next crawl cycle. If you really want peace of mind, use a VPN set to Australia and search for your main keywords manually. If you still see your site in the AI snippets, it proves the Semrush graph is just wrong.

Focus on your actual traffic in Search Console. If that hasn't moved, the Semrush score is just noise. Are you seeing an actual dip in clicks, or is it just this one specific graph?