If you hear a clicking under the hood when you press the horn button on the steering wheel then the relay should be working. Check the voltage at the horn connection when the horn button is pressed. To check the horn, run a jumper wire from the positive post to the horn's connector. (You can also remove the horn from the car and put the connector tab on the negative post and the jumper wire on the positive.)

The relay could be working but still not providing voltage to the horns. It could have a burned connector inside. If you have voltage at the horn connector then the horn is bad.

On an old '91 Camry I had both horns quit at the same time. Sounds strange but they did. I replaced the relay and nothing. I checked voltage at the horn and it was 12.7 vdc. I bought new horns, problem solved.