From what I've read in other posts, what happens to you may be related to some surround settings which are still active somehow, or a high sample rate configured in your Output Audio device. Immerse Gamepack recommends using 48kHz, while some Soundblaster cards can go higher than this and can cause the sound to get distorted, possibly not sounding. Have you tried reducing the audio sample rate to 48kHz?

So just to make sure, make sure you turn off other spatial audio solutions and headphone options, such as virtual audio mixers, surround sound headphones, and system-wide solutions such as Dolby Atmos or THX Spatial Audio

What is Soundblaster model do you have?