I hate to make these suggestions, but if Carl cannot give you the cables, he should return the money. My suggestion is to go to the police in Montreal, and tell them that you have a merchant located in Montreal from whom you have ordered and paid for merchandise that has not been delivered, and you want to file a complaint. Ask them the appropriate law enforcement agency to go to. They may take the report, or they may tell you which agency handles such problems. You being out of country, they may ask for an affidavit (sworn statement) with your complaint. I have not been connected with Canadian law enforcement, but this is the general method in U. S.
Your problem is that they may regard this as a civil matter, a breach of contract, and tell you to get a civil attorney and sue the guy. There may be a consumer agency analogous to Better Business Bureau. If you went through Ebay and Paypal, you may have recourse there. I am so sorry to hear about all this difficulty, because I had good results, if slow results, and got a good cable. There is yet another awful possibility here. Carl might be totally incapacitated, or dead. Take a look in Montreal Obits and see if his name comes up. If he is deceased, you would have a claim against estate.
And good luck from the old suggester,