Canon error 5100 is a print head error.
Remove all the ink cartridges from the machine
Then clean the contacts on the cartridges as well as inside the machine itself
Do this with a small amount of warm water on a cotton swab until no ink comes off on the swab
If any of the other cartridges are low, empty, leaking or bulging replace them
Then turn off the machine and unplug it for 70 seconds
Plug it back it and wait for the insert cartridges message
Insert the cartridges and check to see if the problem is still there
If it is it means the print head has failed
In order to fix this the print head inside the printer needs to be replaced
The print head is the part of the printer that puts ink from the cartridges onto the page
Unfortunately this can sometimes cost more to replace then the machine itself

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