Hi @[G.T.R] I 289 I Roars
Are you using the latest version of SII Decrypter?
Right click on the decrypter, chose properties, and see if there is a message that the program has been blocked because it has been downloaded from the internet, if yes, remove the block.
I get the best result if I place SII_Decrypt[L64] in the save file i want to edit.