How did the yellow "dry up". did you install the yellow cartridge correctly, ie removed all the packaging.
You may get it back working if you remove the cartridges take out the head an place it on a saucer with a solvent soaked kitchen tissue under it and leave overnight. You can purchase head cleaning fluid from on line stores, windex has been used in the USA.
When satisfied dry the head carefully refit, put the cartridges back on and do a couple of heavy cleaning cycles.
Remember if you at first you don't succeed try again.