2014 Silverado OEM Horn Wire/SPDT Hook Up

Good Morning Everyone.

I did a search and found some similar but nothing that answered my question. Hope someone can help me figure this out. It has me stumped.

2014 1500 Silverado.
Installed the same way as I had on two previous trucks (which DBO was a saving Grace for first install, which the 2nd mirrored)

Using (want to) a SPDT switch. To switch between air horn and OEM horn. Using OEM horn button as the trigger.

Cut BN/WH OEM horn wire at the brown BCM plug. One side is constant hot 12v. Other side is dead.

Ran 12v to horn solenoid
Ran other side of solenoid inside to the SPDT outer prong.

Ran hot side of BN/WH OEM horn wire to other outer prong on SPDT.
Ran dead side of BN/WH OEM horn wire to center prong on SPDT.

Was figuring the center prong would act as the ground and ground out each horn. Like previous installs.

It only actuated the OEM. When I flip the SPDT to the air horn. I get nothing.

If I take a grounded jumper wire and touch the other prong of the SPDT where the air horn wire is. It actuates.

I have tried a few different combinations.
I can add those if you’d like. Post is getting long already… lol! I found this. Just not 100% if it’s correct or telling me completely.