Sometimes my work involves everyday things, and that’s fine. Sometimes my work involves esoteric things where I really gotta reach into my bag of tricks. This was one of those.

I got a call from a client — let’s call him Bill. He’d been able to print to both of the printers in his home, and now he couldn’t print to either one.

This is part 1 of 3, and just the tip of the iceberg.

One of the printers was an HP LaserJet Pro MFP m225dw, a relatively recent model. It showed up on the network when I clicked “Add Printer”, but it refused to be printed to. Looking at the Printer Queue window, I saw there was an error about “Encryption credentials expired.”

This, frankly, is the kind of error no one should ever see, because who could possibly understand what it means? The computer and printer should have a means of talking to each other to address the issue.

And the issue was: macOS uses Secure AirPrint to talk to the printer. “Secure” means encrypted, so that everything going between your computer and the printer isn’t snoopable by someone else on the network. Encryption requires a technology called a certificate, and certificates have expiration dates, which is why you get an error when trying to visit a Web site on a computer whose clock is wrong, or which has a very out of date browser. When a certificate is expired, the connection can’t be made without your explicit approval, or sometimes at all.

So, that’s all well and good, but this is just a printer. It should just work. But it didn’t. I had to go into the printer’s own configuration pages, which you access via a web browser, and deep within its settings I found where you could generate a new “self-signed” certificate. I had to specify some kind of expiration date, so I went with the max, 10 years. After that, all was well.

HP has a page (https://support.hp.com/lt-en/document/ish_7345764-7345853-16) that details this process, but, bizarrely, they suggest you use a Windows computer to fix it. Because you, a Mac user, just have a Windows computer lying around to do this with, obviously. What you have to do is go to Apple Menu > System Settings (or Preferences) > (your printer ) > Options & Supplies > Show Printer Web Page. That will open a web browser, which will probably block you, due to the expired certificate. But if you poke around, you should be able to bypass this. On Chrome, for example, you can click Advanced > Proceed (unsafe) and then you’ll be in.

Then, in the case of this (and most) HP printer, it’s under Network > Advanced Settings > Certificates, and choose whatever options lets you create a new self-signed certificate, replacing the existing one. Make sure that you set the duration of the certificate to the max. Then click Finish, and off you go, printing again.

Apple did such a good job with the printer vendors, getting them to adopt Bonjour for easy printer discovery, and AirPrint for easy configuration with driver installation. Maybe they can have a chat with them about how to, you know, allow them to keep printing without you having to do a deep dive.

Image: From the movie Office Space