Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
When a cartridge is let to dry out, sometimes ink on the printhead for that color of ink, dries out also.
This can mean the printhead needs replacing, sometimes.
But, a cleaning procedure may get it working again, if done as follows:
1. Clean the (magenta) printhead. (This is an operation in your printer's Maintenance functions, to be found in your printer's driver in the Maintenance tab, or in your printer's software functions. It may not be specific to the color (magenta), in which case, just choose Clean Printhead(s).)
2. Wait 1/2 hour to several hours or overnight, leaving the printer On but unused (no print jobs, etc.)
This allows waste ink to soak into the printhead and hopefully dissolve dried ink etc.
3. Clean the printhead a second time.
4. Wait again (as in step 2 above) for 1/2 hr. to several hrs., printer On but unused.
5. Clean the printhead a third time.
Then test whether magenta ink is showing up at all in prints at this point. If it is, even faintly, then repeating this procedure will (eventually, at the cost of a certain amount of ink wasted in the process) clear up the clogged printhead.
After that fails, if it does fail, what you need to do is to decide whether replacing the printhead (which will cost something considerable, more than you would think usually) is better, given the printer's age, or whether it would be more preferable for you to replace the printer altogether with a new one (and hopefully recycle the old printer, always a good idea.)
So try the triple-cleaning-with-wait-times that I recommended, and get back to me if it doesn't work for you (so I can advise you further...)... or if it does help (- I always like to hear that something I recommended has worked!)