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I’m sorry to hear you're having trouble. I know that can be frustrating. Hopefully, we can get this resolved quickly
5B00 means waste ink absorber is full and needs to be replaced. Your printer has a waste ink absorber which takes in waste ink during the printing and some other operations like print head cleaning or nozzle cleaning. The printer will keep the amount of ink that the absorber has absorbed in its lifetime.
After the continuous use of the printer, the printer will enter a condition when the ink absorber is almost full or completely full. In this situation, the printer itself will prevent you from printing to protect itself from further problems like overflowing, bad prints, etc. That is why it is showing that error. You need to call the Canon technician to get it cleaned or replaced.
Replacing or cleaning the printer absorber is a messy and time-consuming process. Sometimes cleaning will not do anything and you may need to replace the absorber and requires an hardware reset. It is done by the manufacturer and this is something that the consumer shouldn't do. This issue can't be fixed easily as this require part replacement or reset from the manufacturer. So, you need to take it to Canon and have them replace the absorber and/or reset the waste counter using their tool (which is not available to customers)
If this is an old model printer, I'd recommend not to fix it as it may cost more than $50 to replace the ink pads/absorber. You should get a new printer because it has more life for other components than the current printer and you will get a fresh warranty as repairing/replacing existing components doesn't give that. Not only that, for the price of fixing this printer, but you will also get a current generation printer.
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