There is a simple way to determine what and where the problem lies.

If you hear the relay working,that leaves only the wire from the relay to the horn(s). or the horns themselves.
If,,,,,,,, you connect your test light ground clip to a good ground, stick the pointed end of the light into the plug at the horn terminal , depress the horn pad, the test light should lite If it does the problem is with the horn(s). If it doesn't light there is a break in that wire from the horn relay down to the horn..
What we do is stick a rag into each horn, so you don't become a nuisance, or go deaf, you can use a piece of insulated wire to bring power from the battery positive terminal down to the tab on one of the horns , it should blow ! If not ,sometimes a rap or two will loosen up the vibrating plate inside the horn and it may start working. Just be very careful when bringing that wire to the horn that you do not touch any metal part of the vehicle ONLY THE TERMINAL ON THE HORN, or you could do some welding.
You will know if the horn is capable of working or not.
Many times the horns get exposed to moisture and road dirt and freeze up internally and sometimes the rap or two works.

 

Ok I crossed out everything with red that can be eliminated.
Remove the horn relay.
Check with a voltmeter that you have 12V at pin 3 of the relay(Orange arrow), just to make absolutely sure.
Jump 12V from the battery to pin 5 of the relay(Blue arrow), note if the horn blows or not.
Using a short piece of wire jump between relay pin 3 & 5(Green arrow), note if the horn blows or not.
Remove the horn itself and apply 12V to the red wire pin and a ground to the black wire pin, note if the horn blows or not.
Below you will find a picture of different types of relays and their pin numbers.

Are you aware of how to test the resistance of a wire?

 

Thanks again 'scott.butler4', and also to 'hanky' for all the help and advice. Gonna scrounge up a jumper wire to bypass the wire from the junction box to the horn itself. The information on the relay. shows me that we have the Basic 5 Pin Micro Relay, and now I know what pins are which so I can continue troubleshooting. I have to be honest, this troubleshooting might seem simple to other but its pretty fascinating to me. Of course, I have been cooped up inside since last March because of covid so doing anything outside that is meaningful is a treat. Anyway, I will keep you guys in the loop after doing my testing.

 

You can just use a paperclip as a jumper for where the green arrow goes.

 

Found a metal paperclip and jumped the 3 to 5 (connections after removing the relay). No horn noise after connecting the 3 & 5 with the jumper. My son has all my testing equipment in his car so when he comes over again I will ask him for help. I did manage to drop the relay somewhere in the truck engine compartment, when I pulled it out. Will ask my son to find that as well. In any event my guess right now is a broken positive wire somewhere from the horn to the junction box. I wonder if there is a way to run a new wire inside the wire loom to the bottom of the relay in the junction box down to the horn positive (+).??

By the way, do you know what florescent UV engine oil dye I can use that isn't the same yellow/green color used in the cooling system? I already put some of that in the coolant to check for any leaks and i want to do the same in the engine oil. I know there are leak detection kits that have different color florescent UV dyes for the different automotive fluids but I can't afford a kit. A very old neighbor, who is a long retired mechanic, said he knows there are UV dye colors like blue, red, & white, but he can't remember much more than that . I asked the girl who answered the phone at the local auto-zone about engine oil UV dye's and she said she didn't know of any color but the yellow/green. Thought i would ask here.

 

You are correct that it will be a broken wire between the relay output and the horn, I just like to 100% rule out everything else by checking with a voltmeter.
Yes you can run a new wire from the relay to the horn, its called a overlay.
The correct way is to cut open the harness, locate the correct wire, check resistance to find the open and then cut open the harness further along the correct way.
The issue with a overlay is that there may be other wire damage at that location that you would find if you actually locate the open.

 

No idea about the leak dye, only ever seen the bright green stuff.