18.04 and Brother MFC-7420 USB printer - doesn't print
Solution 1:
I had a similar issue with my DCP-7055 after upgrading from 16.04 to 18.04. Installed / reinstalled CUPS and used the Brother installation script. Even the scanner worked! Through the looking glass.
My issue was fixed by following the answer here, "18.4 - Printer 'Filter failed'.