In case of the PRO-9500 I don't believe @rodbam's nozzle pattern will heal, it is an electrical failure.Every once in a while, you can pick up a Pro-10 for $99 from a place called Murphy's camera in the USA. Even with the cost of reshipping it might be worth it. Only trouble is that you will have to have a friend in the USA to send the rebate to. A commercial reshipper address might even suffice I suspect so it might be viable for international customers. At $99, a new Pro-10 is less than the cost of a new printhead for a 9500. Apparently this last Christmas season the deal was to be had again. Yeah, the deal is/was real.
I will add one comment on the nozzle pattern. One of my iP4500s was displaying a similar pattern, but for the purpose for which I was using it, it did not matter much. Then after a few months. It was good again. Why? I don't know. But soaking is not always the last physical thing to try. Sometimes nozzles can be restored/cleansed/blasted clean with a proper cartridge and OEM ink. When how and why? Desperate times call for desperate measures that sometimes work without a known reason why.
Don't throw away the old printhead. Physically flush with some light pressure thoroughly before putting it away. You never know down the road.