Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
First we can reset your printer and see if it works or not.
After resetting, your Printer will disappear from the list. Click the + button in there and add it back. Please let me know if that didn't work, so we can continue troubleshooting
Before you add it, just restart your printer. The plus is at the left bottom of that list.
Also I want you to go to printer settings and make sure it has active wireless connection.
See this picture --> http://www.howtogeek.com/wp-content/uploads/2014/06/650x486xadd-network-printer-on-mac.png.pagespeed.gp+jp+jw+pj+js+rj+rp+rw+ri+cp+md.ic.o5AD8TqZOo.png
On Printer (it it has LCD screen), open Setup > Network section or Wireless secion and make sure it is still connected to your WiFi