Siri not hearing Studio Display microphone on Mac mini

I have a 27" Studio Display connected to an M4 Mac mini running MACOS 27. SIRI AI does not hear the Studio Display mic. The little bubble appears and then disappears. If I open the SIRI app, the mic in the new conversation dialog is inactive. The mic works well with other apps like Voice Memos and QuickTime. I think I have the SIRI settings enabled correctly, but I can't get SIRI to hear me. What am I doing wrong?

Thanks