Brother HL 2270DW - Manual (Page 115)

Troubleshooting
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q Put the toner cartridge back into the drum unit until you hear it lock into place. If you put the cartridge in
properly, the green lock lever will lift automatically.
r Open the front cover. Put the drum unit and toner cartridge assembly back into the machine.
s Close the front cover.
t Make sure that the Error LED is off and that the Ready LED light is on. If the machine does not start
printing automatically, press Go.