Ardour 8.7 will not accept Carla Rack

I’m running Ardour 8.7 on a fresh install of Ubuntu Studio 22.04.1. The audio engine is JACK/Pipewire, thought I also tried ALSA. I tried to add a Carla Rack to Ardour (from the default Ardour plugin list). When I do, I get the following error message in the log: “2024-09-29T16:29:07 [ERROR]: LV2: Failed to instantiate plugin http://kxstudio.sf.net/carla/plugins/carlarack”. Carla itself will start, and I can load plugins into Carla.

Any thoughts as to how to fix this? BTW, I can load Carla on Ardour 8 as it is installed in Ubuntu Studio.