Hello my name is Sheldon and I am a Brother customer executive. To fix an Brother printer offline on a Mac , make sure it is turned on and correctly connected to your network or system. Check the printer's status in the print queue and clear any pending work. If the printer continues to fail, restart both the printer and the Mac. If the issues continues, make sure the Brother printer driver is up to date and properly installed. Re-add the printer or reinstall the driver.