Before you replace the cartridge, place a strip of selotape over the holes on the bottom or the cartridge may not function correctly.
They should not be removed until registering empty.
That is the sole reason why i dumped my 790. The only way to refill them is by using a "chip charger" which resets the chip so it registers full.
Your printer stopped working because a cartridge was empty, the "clone" cartridges probably had not been reset so they didn't work.
If you want to continue with this printer and run it cheaply, then you need the Zap-it kit from JR Inkjet:
http://www.jrinkjet.co.uk/ZapItInfo.htm
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