Printer issues can be due to overload, or perhaps it may be an issue with the driver, or the network may be undergoing some connectivity problems and also loose connection might be the culprit. Trouble can happen anywhere along the line, a system hardware failure cannot also be discounted. The problem is diverse and only a critical assessment can pinpoint the actual cause, so remedial measures can be taken up.
Source: Brother printer offline
Click on the Start button on your computer, and then click on the Devices and Printers option. Now right-click your Brother printer icon and click on the See What's Printing option on your screen. Click on the Printer option at the top of the window > look for the check mark in front of the Use Printer Offline option.