Place cauliflower on a trivet in a multi-functional pressure cooker (such as Instant Pot®). Add chicken broth; close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 4 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid.
While pressure is releasing, mix cream cheese, sour cream, butter, and ranch dressing mix together in a small bowl.
Transfer cauliflower to a large bowl. Add cream cheese mixture and toss to combine. Puree with an immersion blender until smooth and creamy.