Hey, based on that error message, it sounds like you're using Inter-App Audio.
To select AUv3, in the dropdown list you should select the green-colored app name, not the blue-colored app name. This will load the plugin as an AUv3 instance inside of Auria, instead of opening the app separately and routing audio to it as Inter-App Audio. AUv3 should be much more stable, and you can use multiple instances.
