Printers work offline when they have a hard-line connection to the computer holding the document. The printer requires a means of communicating with the computer so it can read and transmit from the ...
If you are unable to print to your installed Brother printer because it is appearing as offline, then you can adjust some of the printer's settings so that you are able to continue printing documents.
Your printer may be offline because it has many moving parts, and there are many different ways it can fail. Possible solutions to an offline printer include checking your printer's WiFi connection, ...