After downloading the firmware file I had to convert the downloaded file from a sihp1020.img file to 1020.dl file
I used this command: sudo arm2hpdl sihp1020.img > sihp1020.dl
Then I had to copy it into /usr/share/foo2zjs/firmware/sihp1020.dl
Then I switched the printer on, and added the printer to the computer printers and it worked
After downloading the firmware file I had to convert the downloaded file from a sihp1020.img file to 1020.dl file
I used this command: sudo arm2hpdl sihp1020.img > sihp1020.dl
Then I had to copy it into /usr/share/ foo2zjs/ firmware/ sihp1020. dl
Then I switched the printer on, and added the printer to the computer printers and it worked