Horn not working

So my 19 year old put a bad boy airhorn from Harbor freight on his Ford Ranger.
And bought me one for a present.
He did the install on his Ranger.
So I let him start mine.
Disconnected stock airhorns plugged in new one wolo horn worked with ground to battery didn’t have the relay it comes with in use.

went to show me the sound and now the horn won’t work put everything back together no horn. check the fuse Ok
relay? Is there another fuse somewhere possibly under the dashboard everything else works but the power mirrors.
thanks
Don

 

Here is the Horn circuit. Hope you can read it.
Get your multimeter, put 1 lead on battery negative, and the other on the horn lead, push the horn button. If you get +/-12V it's a bad ground at the horn. If not the horn relay and fuse are in the fuse box in the engine bay.

 

Does the horn work when you hit the panic button? Based off what you said should be a output problem but just throwing this out there, just a easy test to do.
What the guy above said will work for diag if you know how to use a voltmeter.