DIAGNOSIS When the scanner loses connection, it's almost always a software or network issue on the computer side, not the printer hardware. The Brother scan drivers or services have crashed or been blocked.
FIX First, restart both the printer and your computer. If that doesn't work, re-run the Brother software installation and select 'Change' or 'Modify'. Ensure the 'Scanner Driver' and 'ControlCenter' components are selected for installation. This often repairs the link without a full wipe.
IF THAT DIDN'T WORK If you're on a Windows PC, check if the 'Brother BRAdmin' service is running. Open Task Manager > Services, look for 'BrSfcService' or similar, and ensure it's running. Sometimes a Windows update or firewall resets permissions.
HEADS UP If you're scanning over WiFi, the connection can go to sleep. Try pressing the 'Scan' button on the printer's control panel to wake the network connection before initiating a scan from your PC. The 'check connection' error often just means it's momentarily asleep.