Add all seasonings to a small bowl. Combine all spices using a whisk (or fork) – making sure to break up the brown sugar.
Add chicken broth and 1 tablespoon of the seasoning mix to the Instant Pot.
Next, add the sausage, potatoes, and corn to the pot and mix them well. Lock the lid and cook for 4 minutes at high pressure.
While the pot is cooking, defrost the shrimp (if frozen) in cold water, then drain completely.
Once cook time is complete, quick-release the pressure.
Remove the corn, potatoes, and/or sausage and set aside. Switch back to the sauté setting to bring the mixture back to a boil. Add lemon juice, butter, and one more tablespoon of seasoning mix.
Add the shrimp, making sure they are submerged in liquid. Once it comes to a boil, switch back to "keep warm" and stir occasionally until the shrimp are pink and opaque and the tails are slightly red. This will take 5 to 10 minutes.
Return the corn, potatoes, and sausage to the pot, along with the remaining spice blend, and mix well. Serve immediately, pouring some of the extra broth over the top for added flavor.