You can try the following techniques to resolve your brother dcp-l2540dw offline issue:
• Check to see whether the Brother Printer is turned on and if there are any problems shown on the screen. • Make sure your Brother Printer is configured as the default printer in Windows 10. • Delete all print jobs from the printer properties option. • Remove a duplicate of your Brother printer's icon from your computer (for example, Brother XXX-XXXX (Copy 1)).