You’ve already done the right basic troubleshooting, and your testing strongly points to macOS Tahoe itself being the cause, not your network or hardware.
Since:
- AirPlay works from iPhone and iPad
- AirPlay works from another Mac running macOS Sequoia
- AirPlay fails only on the iMac running macOS Tahoe
- Safe Mode and resetting AirPlay/audio services didn’t help
this is almost certainly a Tahoe AirPlay bug or compatibility issue, especially with AirPort Express (older AirPlay 1 devices) and Apple TV HD.
Things still worth checking (if not already):
- System Settings → General → AirDrop & Handoff
- Make sure AirPlay Receiver is enabled.
- System Settings → Privacy & Security → Local Network
- Ensure apps like Music and System Services are allowed.
- Firewall
- Temporarily turn off System Settings → Network → Firewall to test.
- Make sure all devices are on the same Wi-Fi band (2.4 GHz vs 5 GHz).
Reality check:
AirPort Express is no longer supported, and Tahoe may have changed AirPlay networking or audio frameworks. Apple has historically broken AirPlay to older devices in early macOS releases.
Best next steps:
- If Tahoe is beta: submit feedback via Feedback Assistant (this is important — Apple does fix these).
- If Tahoe is public release: contact Apple Support and reference that AirPlay works on Sequoia but not Tahoe.
- If AirPlay is critical: the only guaranteed fix right now is downgrading to macOS Sequoia until Apple patches Tahoe.
You’ve ruled out user error and configuration issues — this is almost certainly on Apple’s side.
