Brother HL-L8350CDW "Invalid Certificate" Error: What It Is and How to Fix It

Last updated: September 25, 2026.

Quick answer: A Brother HL-L8350CDW "invalid certificate" (or "bad certificate" / "unable to verify printer") error almost always means your Mac or PC doesn't trust the security certificate the printer uses for encrypted (IPPS/AirPrint) printing, usually because it's self-signed, expired, or the printer's clock is wrong. The fastest fixes: set the printer's date and time, create a new self-signed certificate in the printer's web settings, or re-add the printer on your Mac using the Brother CUPS driver or the LPD protocol instead of Secure AirPrint.

If you own a Brother HL-L8350CDW, or a related Brother color laser such as the HL-L8260CDW, MFC-L8610CDW or MFC-L8900CDW, and you've tried to print from a Mac on a recent version of macOS, you may have hit this: the printer won't print, invalid certificate. The queue stalls and the message doesn't say what to do. It isn't a broken printer. Here's what's happening and how to fix it in 2026.

What Does "Invalid Certificate" Mean on a Brother Printer?

Network printers use a digital certificate to prove their identity when your computer prints over an encrypted connection (IPPS, used by Secure AirPrint). The HL-L8350CDW, released around 2014, ships with a self-signed certificate that isn't issued by a trusted authority. Newer versions of macOS are stricter about untrusted certificates, and certificates also have an expiry date. If the certificate is untrusted, expired, or the printer's clock is set wrong so the certificate looks invalid, macOS holds the job and shows a certificate error.

The printer isn't doing anything malicious, and the certificate isn't counterfeit; it just doesn't meet the bar your computer enforces.

Fix 1: Check the Printer's Date and Time

A wrong clock makes a valid certificate look expired or "not yet valid." On the printer, go to Menu > Initial Setup > Date & Time (or set it in Web Based Management under Administrator > Date & Time, ideally syncing with an SNTP time server). Then try printing again.

Fix 2: Create a New Self-Signed Certificate on the Printer

If the certificate has expired, generate a fresh one:

1. Print a network configuration report (Menu > Print Reports > Network Configuration) and note the printer's IP address.
2. Type the IP address into a web browser to open Brother's Web Based Management and log in (the default password is on the printer's label or "initpass" on many older models).
3. Go to Network > Security > Certificate and choose Create Self-Signed Certificate. Keep the common name as the printer's IP address or network name.
4. Under Network > Network > Protocol (HTTP Server Settings), select the new certificate for IPPS/HTTPS and submit.
5. Restart the printer, remove it from your computer, and add it again.

Menu names vary slightly by firmware version.

Fix 3: Reset the Mac Printing System and Use the CUPS Driver

1. Open System Settings > Printers & Scanners.
2. Right-click (or Control-click) in the printer list and choose Reset printing system. This removes every printer.
3. Click + (Add Printer).
4. Select the HL-L8350CDW, then change the Use dropdown from AirPrint or Secure AirPrint to Brother HL-L8350CDW CUPS (install Brother's driver first if it isn't listed).
5. Click Add.

The CUPS driver doesn't rely on the Secure AirPrint certificate check. You may lose a few AirPrint conveniences, but printing will work.

Fix 4: Add the Printer by IP Address Using LPD

1. Note the printer's IP address from the network configuration report.
2. In Printers & Scanners, click +, then the IP tab.
3. Enter the IP address and set Protocol to Line Printer Daemon – LPD.
4. Leave Queue blank, choose the Brother CUPS driver under Use, and click Add.

LPD doesn't validate certificates, so it sidesteps the problem. You can also use plain IPP (not IPPS). Both are unencrypted between your computer and the printer, which is fine on a home network; in a corporate environment, check with IT first.

Fix 5: Update the Printer's Firmware

Brother has released firmware updates for many models that improve security and certificate handling. Visit Brother's official downloads page, enter your model, choose your operating system and look for the Firmware Update Tool. After updating, generate a new certificate (Fix 2) if the error persists. Note that firmware updates can also change how the printer handles third-party toner; see what printer firmware updates change.

How Do I Fix "Invalid Certificate" on Windows or iPhone?

Windows: Windows rarely shows this error for standard printing. If Brother iPrint&Scan or a browser warns about the certificate, you can install the printer's certificate as trusted, or re-add the printer with the Brother driver over a standard TCP/IP port. If the printer won't print at all, reinstall the latest driver. iPhone/iPad: AirPrint from iOS uses the same certificate; setting the correct date and creating a new certificate (Fixes 1 and 2) usually resolves it.

Does This Affect Other Brother Printers?

Yes. Owners of other Brother lasers and inkjets, including models like the MFC-L3780CDW, HL-L3290CDW and DCP-T720DW, report the same "invalid certificate" or "unable to communicate with the printer" messages on Macs. The same fixes apply; only the menu paths differ slightly. For general connection problems, see why your printer keeps going offline.

What Toner Does the Brother HL-L8350CDW Use?

The HL-L8350CDW uses Brother's TN-331 (standard), TN-336 (high yield) and TN-339 (super high yield) toner in black, cyan, magenta and yellow, plus the DR-331CL drum unit. Castle Ink carries compatible TN-336 high-yield toner in black, cyan, magenta and yellow at $45.95 each. For other Brother lasers, see our guides for the HL-L2350DW and MFC-L2710DW.

Brother Certificate Error FAQs

Is the "invalid certificate" error dangerous?

No. It means your computer can't verify the printer's identity for encrypted printing. On your own home network, it's a compatibility issue, not a security breach.

Why did the error start suddenly?

Usually because a macOS update tightened certificate rules, the printer's certificate expired, or the printer lost its date and time after a power outage.

How long is a Brother self-signed certificate valid?

It depends on the model and firmware; many are valid for several years. When one expires, create a new one in Web Based Management.

Can I just ignore the warning and print?

On some systems you can choose to trust the printer when prompted. If macOS won't let you, use the CUPS driver or LPD method above.

Does resetting the printing system delete my other printers?

Yes. It removes all printers from your Mac, so you'll need to add them again.

Bottom Line

The "invalid certificate" error on the Brother HL-L8350CDW is a certificate trust problem, not a printer failure. Fix the printer's clock, create a new certificate, or switch your Mac to the CUPS driver or LPD, and you'll be printing again in about five minutes.

See also: printers that don't lock you into OEM ink | printer ink cost calculator | compatible Brother toner