Did you configure your scanner first. After installing drivers, if system doesn’t see it maybe try configure it in terminal:
Add network scanner entry
Command : brsaneconfig4 -a name=(name your device) model=(model name) ip=xx.xx.xx.xx
Confirm network scanner entry
Command : brsaneconfig4 -q | grep (name of your device)
Open a scanner application and try a test scan.
If i remember correctly, “Scan key tool” (brscan-skey), is only additional tool for scanning direct to email and such. I don’t have Brother printer anymore ( and i had different model), but hope it will help.