Existing Performance Max Campaign

I have managed to successfully connect my site with my Google Merchant and Ads accounts, but my existing Performance Max Campaign doesn’t show up. Instead, the plugin just wants me to create a new Performance Max Campaign.

It’s not worth it for me to create a new campaign just so it integrates with the plugin—as far as I can tell that would just add some convenience of seeing the stats without having to log into Google Ads. But I was under the impression that that was pretty much half the point of this plugin.

I scoured the documentation but I could not find anything to help me resolve the issue. Am I overlooking something? Is this a bug? Is it just a limitation of the plugin?

Thanks.