Canon Pixma IP8500 and iMac

I have an iMac, 4GHz, 24GB memory running El Capitan. I also have, among others, a Canon Pixma IP8500 which is a fantastic printer, but it now won't work with my Mac. It did until a furniture shift-around a week or so back which necessitated disconnecting it from the computer but now it will not do anything. It is not recognised or even seen by the computer.

Any ideas please.