Horn and screen not working

[ItsMeCarlos]

I have a 2023 A5 and was changing out the horn and now the horn doesn’t work anymore (neither the new one or the one that came with the car). The screen also stopped working. I checked the fuse and it’s fine. Now sure what other things to check. Relay also seems fine. 
 

Looking for advise on what else I should check to fix this.

 

thank you!

[Magnet]

Hello Carlos,

Welcome, and thanks for joining.

Would I be daft to suggest even the horn has to be coded in on this virtually new car? 
Kind regards,

Gareth. 

[Steve Q]

Is it an aftermarket horn? 

Why was the horn changed?