SoundBomb™ Mini Electromagnetic Low Tone Horn troubles

On those little horns, you need to follow those install notes EXACTLY. To include using the supplied silver tabs.
Here are the install notes for reference;
http://d1l4i7f87txqmq.cloudfront.net/Installation%20Instructions/Denali/DENALI%202.0/Instructions_TT-SB.10200_rev02.pdf

It sounds like you may have over tightened it.
The install notes only call for 9 nm of torque.
When those are over tightened, they can not vibrate and sound off well or will blow the fuse.
Loosen the bolt you tightened on during the installation.
This happens ALL THE TIME.
These horns have less than a 1% defect rating...
I have a hunch, its just over tightened.

If this is not the issue, kindly check how many amps your OEM horn harness is supplying, if its not 5 amps going to the horn, there will be issues like you describe. The resolution is powering the horn from the battery directly using something like this;
https://denalielectronics.com/collections/horn-wiring/products/dnl-elc-10000
Here are those install notes;
https://d1l4i7f87txqmq.cloudfront.net/Installation%20Instructions/Denali/Soundbomb/Instructions_DNL.ELC.10000_rev00.pdf