Check fuses/relay and all. My Matrix horn quit on me so I put a Fiam in but the connector was different so I cut the OEM connector off and used a spade connector that I had laying around. Worked fine for about a year then quit. I removed horn and connected to battery, worked fine, Checked relay, fuse took horn cover off steering wheel and all looked good. Looked at spade connector I had used and it was dull in color, snipped it off and installed a new one and bang! Horn works fine!
You never know!