Do not take an offense to this please. You can mute your diamond saber by holding down the button and then trigger flash on clash twice while still holding the button. The saber's lights go off and tilting the blade down mutes it. Lift the blade to increase sound then press the button once to exit the volume adjustment menu.
The other thing to check is in the ultra sabers menu. Make sure the volume sliders are turned up for ALL sounds. You can increase the volume for every single effect individually. So if you lowered the effect volume while creating the font, then it does not play at all. You might have even clicked the mute effect button that is located above where the sound file is displayed while editing an effect.
I would check those two things first! If you have no luck with that let me know. I'll trouble shoot it with ya.