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Open the top of the machine, and don't put any paper on the glass sheet.
Do a photocopy. Does the scanner bar, under the glass, light up at all? or is it dimly green-white, rather than blindingly white, when the photocopy process is being run through?
If the scanner bar isn't bright white, or doesn't light up at all, then unfortunately the scanner bulb may be burnt out... or something else associated with it is defective. In which case, you cannot fix it yourself but will have to have the copier function restored by a Canon-skilled repair tech, who can do the rather elaborate disassembly and replacement and reassembly after testing.
(Unless, of course, you are yourself a Canon-skilled repair tech, or something near that level of ability needed for such a repair.)