[Info] Can someone give me some insight

Hello, RaGEZONE I posted here a little bit ago asking about an unknown error I was getting at the login screen of (MapleStory beta v40) I got the Handshake packet to work, but upon login It would either close the client or give me a error having to do with a failed packet check. I looked into this and figure out in MaplePacketDecoder.java it checks the length, version and IV of the packet. What i'm confused about is why this is happening, I considered the encryption was wrong, I looked into many sources and the "KEY" is usually, for the most part the same. But I feel like either there is something wrong with the encryption or the client has some encryption on the login and password like MapleSEA if i'm correct? I'm just not understanding this because if it's Maple v40b thats gMS. so why would the encryption be different ? other than what i saw for v118 tho, can someone give me a little insight on the encryption, or maybe it's not the encryption maybe i'm completely wrong lol, I just want a little info :blink: - Thank you !
p.s. sorry if my writing is a little repetitive.