Thanks for all the comments and help.
There are no other malfunctions, no warning lights, cruise and the phone controls work fine. It's just the horn not blowing. My guess is that there is a brake in the cable from the clock spring to the fuse box (relay).
Tomorrow afternoon I will take it all apart following Steve's instructions. On the left side of the steering wheel is the phone controls panel I think it can be taken off to find the exact screw as described.
I will post the results here.