I think this probably has to do with a network issue. Have a desktop running Win 7, laptop running Win 10, and a Canon MX-490 wireless printer. Everything has been working flawlessly, and have been printing over the wireless network from both computers for quite some time.

Now when we attempt to print the box pops up and says "Another computer is using the printer." No such thing is happening, of course, but the printer will not print. Turn the printer off and back on and not only can the Win 10 laptop print, but the earlier failed print job from the Win 7 desktop then prints. After that, another attempt to print from the Win 7 desktop gets the "Another computer is using the printer" message again. Turning the computer off and back on does nothing.

The only change in the network or to anything in the system was the addition of a Sony smart television to the wireless network. Probably a dumb question, is the television trying to use the printer?