@jay_s_uk @Phaedrux - Thanks for taking time to reply. I followed the process using BOSSA and it seems to have worked.
FIRMWARE_NAME: RepRapFirmware for Duet 3 MB6HC FIRMWARE_VERSION: 3.1.1 ELECTRONICS: Duet 3 MB6HC v1.01 or later FIRMWARE_DATE: 2020-05-19b2
Cheers,
Christian