Triangle Ink has a
MSS Flushing Solution cartridge for that machine
no guarantees that you'll recover a printhead with it, but it should break-down & flush whatever ink its able to make contact with.... I've heard of people also using ultrasonic jewelry cleaning tools with the flushing solution, but that sounds like another potential for getting solution on the electronics of the printhead & ruining it anyways.
uncertain if the jv33 has a capping station that you can fill with cleaning solution, but my jv3 had a nozzle wash mode where it would allow me to fillup the capping station with cleaning solution, and it would park the heads on it for a set amount of time that I would extend by simply pulling the plug on the machine and let the head remain parked on the cleaning solution over the weekend.