Your horn ring is not making contact with the ends of the wires, so you are not making contact with ground. The easiest way to solve this problem is to take off your horn ring, and get an old (or new) glass tube fuse and break out the glass. Now, with the two metal round and hollow ends, slip them over the ends of the contact points. That will take back the eroded space, and the ring will now make contact. Sometimes this method works, and other times it doesn't. If it doesn't, you are out the cost of a fuse and an interesting experience in how your horn works. If it does, you have fixed your horn for about a quarter. Don't get frustrated. If you need for it to be inspected and your horn still doesn't work, just get a push button horn contact from the parts store and mount that on the steering column temporarily. There is no law that says the origingal horn has to work. That will buy you time to do it right, and replace the entire wiring system for the horn.