[Cena44]

pawn Код:

if(!strlen(inputtext)) return ShowPlayerDialog(playerid, DIALOG_REGISTER, DIALOG_STYLE_INPUT, ""COL_WHITE"Register",""COL_RED"You have entered an invalid password.\n\n"COL_WHITE"Type your password below to register a new account.","Register","Quit");

You placed that under the registering dialog response, the script has no other copy of the password, so it can't compare and always returns positive. Move that line under the login response and try again.