Paper jam. caused error print unable 30

"Machine Error 30" (or "Unable to Print") indicates either a simple problem such as a paper or part of a paper stuck inside the machine, which of course is solved by opening the machine as much as possible and remove the reason for the jam.
Even a ripped part of a paper will be able to cause the paper, so it's important to be careful when taking jammed paper out to not rip the paper (do this by carefully pulling the paper among the same way as it would go when printing, not the opposite direction).

However, if that doesn't work, the error is mechanical (but still most likely caused by the jam, either a sensor getting dirty and unable to do it's work, or actually getting broken), and there isn't much you can do. If the message comes back right after turning on the machine, you'll have to have service performed on the machine.