Invalid species number :(

Hi so I just finished designing this rad design for a shuckle evolution and I put all it's stuff in the pokemon.txt. when I playtest it, I try to debug it into my party but my pokemon won't show up. Then I tried replacing the legendary decoys encounter with it and all of a sudden, it says species number (0 of 649) is invalid or something even though I triplechecked everything on the pokemon.txt and graphics to make sure my poke.on was at 650. Pls help bc I'm lost up in here

Have you looked at those similar threads:

https://www.pokecommunity.com/showthread.php?t=360221
https://www.pokecommunity.com/showthread.php?t=409126
https://www.pokecommunity.com/showthread.php?t=362891

Most likely your pokemon.txt file contains errors or you did not compile your game before playtesting. It might also be that your pokemon.txt file is not compatible with the Essentials version you are using.