Add all seasonings to a small bowl. Using a whisk (or fork), combine all spices – making sure to break up the brown sugar.
Add chicken broth and 1 tablespoon of seasoning mix to pot. Next, add sausage, potatoes, and corn to pot and give a good mix. Lock lid and cook for 4 minutes at high pressure.
Meanwhile – defrost shrimp (if frozen) in cold water, then drain completely.
Once cook time is complete, quick-release pressure. Switch back to sauté setting to bring up to a boil. Add lemon juice, butter, and one more tablespoon of seasoning mix. Mix well, making sure that butter melts in liquid below.
Finally, add shrimp and remaining seasoning mix, making sure shrimp are submerged in liquid. Finally, add shrimp and remaining seasoning mix, making sure shrimp are submerged in liquid. You may need to remove some corn, potatoes, and/or sausage in order to do this. (The corn, potatoes and sausage are already fully cooked at this point, so any that you remove can simply be added back in at the end.) Switch back to "keep warm", return lid to pot, and let sit until shrimp are pink, opaque, and tails are slightly red. This will take anywhere from 5 to 10 minutes. Then serve and enjoy!