Hello ckravetz13,
Welcome to Apple Support Communities. Since it sounds like this only happens with select contacts, it is likely due to a setting. First, if you use Focus, make sure that these contacts are allowed. Check out Use Focus on your iPhone, iPad, or iPod touch - Apple Support for assistance.
If you use a different ringtone or text tone for these contacts, see if changing it gives you a different result. Use guidance in Change message notifications on iPhone - Apple Support if needed. That article can also help if those conversations have accidentally been muted. We hope that helps.
Take care.