Haillynka

So Let's go is my first pokemon game I've played, I downloaded PKHex and tried to add Oddish to my box since I can't get him with Eevee version. No matter what I do, I always get the "Your data is corrupted. Please delete the saved data from your system." screen even though it says the pokemon is legal. Any solutions please? It's the first time im using the program so it's pretty probable I've missed something.