Nozzle check, what's missing? Clean, check, clean check, clean check.
If that doesn't work you can soak the park pad with windex and leave
the head on it over night. If that doesn't work then it's a possibility that
the head is dying. Usually though, they go one nozzle at a time, so if you have more
than one nozzle missing it's likely just a clog. Newly hot weather will do this
to printers.
We recently retired a 9000 that was finally going. One nozzle would not clear
no matter what we did. It's a sad day, but these things happen.