I'm puzzling over this one. I've installed all the drivers and packages recommended by Brother and then gone through this entire post (Brother scanner not working in Ubuntu 16.04 though driver installed) and done everything recommended (includeing sane extras).
I'm running Ubuntu 17.10 The printer is Brother DCP-L2550DW
Scanner still doesn't work. sane-find-scanner finds nothing:
# sane-find-scanner will now attempt to detect your scanner. If the # result is different from what you expected, first make sure your # scanner is powered up and properly connected to your computer.
# No SCSI scanners found. If you expected something different, make sure that # you have loaded a kernel SCSI driver for your SCSI adapter.
# No USB scanners found. If you expected something different, make sure that # you have loaded a kernel driver for your USB host controller and have setup # the USB system correctly. See man sane-usb for details.
# Not checking for parallel port scanners.
# Most Scanners connected to the parallel port or other proprietary ports # can't be detected by this program.
However I get this
$ scanimage -L
device `brother4:net1;dev0' is a Brother DCPL2550DW DCP-L2550DW
Ultimatly, it's not showing up somewhere.
$ brscan-skey -l
DCPL2550DW : brother4:net1;dev0 : 192.168.1.4 Not responded