Had the same USB-mic issue on my MacBook Pro. What fixed it for me was:
• Selecting the mic manually in System Settings → Sound → Input
• Granting mic access in Privacy & Security → Microphone
• Re-selecting the mic inside SoundJack itself
• Trying a different USB port/adapter
Quick tip: sometimes macOS keeps defaulting to the internal mic, so re-selecting fixes it fast.
On a fun note — I made a small meme-APK that turns tech fails (like mic not working!) into quick memes. If anyone wants the link, I can share it.