String AES Encryption and Decryption Non Matching

I'm using the following code to encrypt data using AES algorithm with key as system serial and a string as iv

This is the write function

func writeStringToFile()
{
 do{
                let path = URL(fileURLWithPath: "/Users/Shared")
                let folderurl =  path.appendingPathComponent("MYPATH")
                let systemserial=self.getsystemserial();
                let paddedserial = systemserial.padding(toLength: 16, withPad: "X", startingAt: 0)
              
                let aes1 =  try AES(key: paddedserial, iv: "mystrongpasscode") // aes128
                let sdata =  try aes1.encrypt(Array(mystring.utf8))
               
                let writedata1 = Data(bytes: sdata)
              
try FileManager.default.createDirectory(at: folderurl, withIntermediateDirectories: true)
                let filepath =  folderurl.appendingPathComponent("MYFILE")
                try writedata1.write(to: filepath)
}
catch
{

}
}

This is the read function

 func readStringfromFile() -> String
    {
        do{
        let path = URL(fileURLWithPath: "/Users/Shared")
        let folderurl =  path.appendingPathComponent("MYPATH")
        let filepath =  folderurl.appendingPathComponent("MYFILE")
        let text1 = try Data(contentsOf: filepath)
        let systemserial=self.getsystemserial();
        let paddedserial = systemserial.padding(toLength: 16, withPad: "X", startingAt: 0)
        
        let aes1 =  try AES(key: paddedserial, iv: "mystrongpasscode") // aes128
            let decrypted =  try aes1.decrypt(Array(text1))
            return String(bytes: decrypted, encoding: .utf8)!
        }
        catch
        {
            return " "
        }
    }

The function i use to get the system serial is the following

func getsystemserial() -> String {
guard case let platformExpert = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IOPlatformExpertDevice") ), platformExpert > 0, let serialNumber = IORegistryEntryCreateCFProperty(platformExpert, kIOPlatformSerialNumberKey as CFString, kCFAllocatorDefault, 0).takeUnretainedValue() as? String else { return "" }; IOObjectRelease(platformExpert); 
return serialNumber
}

But the read and written strings are not matching. What am i doing wrong ?