Unfortunately there is not much that we can do about this problem, the issue is with the printhead and generally it will need replacing. Normally there is Head Cleaning function on the printer itself, this should be carried out 3-5 times just in case the colour in question comes. If not then it will need a new printhead, unfortunately they are not always available though. Have a look online but if you cannot see one then it’s likely not available, even if it is I would question whether it is actually worth replacing or not. Most inkjets are essentially throwaway items so there are plenty of other problems you might encounter which you will not be able to resolve, so if you get this sort of problem you should probably replace the printer. If you have stacks of ink and it is fairly new then maybe there is value in changing the printhead (providing it is available), but if you have had it many years or used it a lot then it’s probably best to replace the printer.