The "Hold for Authentication" error when printing via Bonjour to a shared printer in Sonoma is a known issue. It occurs because macOS requires credentials to access a printer shared from another Mac, but doesn't always prompt correctly. Here's how to fix it:
1. Fix permissions on the host iMac (the one with USB printer) — On the host Mac, go to System Settings > Printers & Scanners, select the Brother printer, and make sure "Share this printer on the network" is checked. Then click the lock icon and ensure the sharing settings allow all users or your specific account.
2. Re-add the printer on the client iMac — On the Mac that gets the authentication error, go to System Settings > Printers & Scanners, remove the existing Brother printer, then click the + button to re-add it. Look for the printer under the "Default" tab (it should show up via Bonjour). Re-add it fresh.
3. Check the queue on the host Mac — You mentioned the queue appears empty when you check the host Mac. This can happen because the job is being blocked before it enters the queue. Open the printer queue on the host Mac, then try printing again from the client to see if the job appears.
4. Use the IP address to add the printer — Instead of Bonjour discovery, try adding the printer via its IP address. On the client Mac, go to System Settings > Printers & Scanners > + > IP tab, enter the host Mac's local IP (e.g., 192.168.1.x), select Line Printer Daemon (LPD) protocol, and use the printer model. This bypasses Bonjour authentication issues.
5. Sonoma-specific fix — Open Keychain Access on the client Mac and search for any saved credentials related to the printer or the host Mac name. Delete any outdated entries, then try printing again — macOS should prompt you fresh for credentials (if needed).
Hope one of these resolves the authentication block!
