三星SCX-4521F出现Front or Rear,Cover Op

三星SCX-4521F出现Front or Rear,Cover Op 传真机出现< front or rear> cover open 打印机显示Front or Rear Cover Open PC Print Pending ` 三星scx-400打印机显示[ Jam 1] or [No Cartridge]打印机无法打印,应该怎么弄? m7020联想打印机出现以下提示:cover is open close the front cover请问是什么意思, the hp lawerjet 1020 front cover door open or the toner cart 打印机出现open the front cover then replace the toner cartridge w mfc-7420出现open the front cover then replace the toner cartri (Q.rear-Q.front+MAXQSIZE)%MAXQSIZE是什么意思 open front cover replace toner Front rear Subwoofer center side Front Green In Rear Blue In 兄弟打印机报open rear cover remoye paper