That's a printer hardware issue.  I assume that is probably an HP printer, which is the only place I've ever seen a 50 Service Error.  It may be the same on other devices too, but I don't know if that's the case.  Anyway, that's an error indicating that the fusing assembly is not reaching the proper temperature to melt the toner onto the paper.  

Turn off the printer and let it sit for half an hour or so. Turn it back on and see if it works after that. If you still get the error message or the thing still doesn't work, you may have to replace the fusing assembly or the AC power supply.  Good luck