Based on user reports, macOS 27 Golden Gate has ‘broken’ printer drivers from several manufacturers. Note that in many cases, this is because those drivers use code for Intel processors and not Apple Silicon – manufacturers like Brother have had 6 years to make the switch, and they've failed to do so. Sorry, but this is not on Apple. See below for the method to buy yourself one more year by (re)installing Rosetta 2.
The Brother MFC-7840W does not support AirPrint, which is the easiest way to connect to a printer and does not require drivers from the manufacturer, only an AirPrint-capable printer.
Rosetta 2 (the macOS engine for running Intel apps on Apple Silicon) is needed for some old printer drivers. Even if it was installed on your Mac previously, the upgrade to macOS 27 Golden Gate removed it for some users (me, included). If Rosetta 2 is not installed and you launch an Intel app, you’ll be prompted to install it. That is what happened here, when I launched an app that I had used frequently on Tahoe then launched for the first time after upgrading to Golden Gate.
That prompt does not happen with a printer driver. Accordingly, it may help to install Rosetta 2 using Terminal. Apple provides instructions for that HERE. The short version is launch the Terminal app (find in Spotlight or in Applications > Utilities) and paste the following, then press return.
softwareupdate --install-rosetta
Note that if this enables your old printer drivers to work, you’ve only put off the inevitable. As the dialog box above indicates, macOS 27 is the last version that will support Intel-only apps (and printer drivers). If you upgrade to macOS 28, you will need to find another solution – either a new printer (get one that supports AirPrint), or for example setting up a Raspberry Pi as a print server (not too hard and plenty of tutorials, but the cost will be similar to an inexpensive printer).
If that does not help, then the first step is to reset your printing system. Note that doing so will remove all your printers and you will need to re-add them, but that is Apple’s suggested method to solve printing problems.
Steps to Reset the Printing System
- Open System Settings > Printers & Scanners
- Secondary-click (right-click, two-finger click) in the top two lines or on any printer and select Reset Printing System
Since your printer does not support AirPrint, check the manufacturer’s website, and if there are no updated drivers, then you may be able to set up your printer on macOS using a generic driver.
Steps to Connect and Print
- Connect the printer: Plug the printer into your Mac using a USB cable, or connect it to your local network via an Ethernet cable.
- Add the printer: Click Add Printer, Scanner, or Fax (the + button).
- Choose Driver: Select your printer from the list. In the "Use" drop-down menu, choose Generic PostScript Printer.
- Finish setup: Click Add to complete the installation.
- More info: Add a printer to your printer list so you can use it on Mac - Apple Support
If that does not work, there are two other options:
Option 1: connect the printer to an always-on host computer (like a Mac, Windows PC, or Raspberry Pi) running third-party print server software such as HandyPrint, Onyx, or a CUPS-based solution to share the printer via AirPrint.
Option 2: you may be able to use the manufacturer’s printing app, which is available on the Mac App Store.
Brother iPrint & Scan
https://apps.apple.com/us/app/brother-iprint-scan/id1193539993?mt=12
