FAES EncryprData and DecryptData returning empty strings?

I’m I missing something? I’ve read that I need to add something to my project’s Target or Build .cs files but I don’t know what that is? any help would be super appreciated!

Code used:

FString MyClass::Encrypt(FString String, FString Key) {

	if (String.IsEmpty()) return String;  //empty string? do nothing

	uint8* Blob; //we declere uint8 pointer
	uint32 Size; //for size calculation

	//first we need to calculate the size of array, encrypted data will be processed in blocks so
	//data size need to be aligned with block size

	Size = String.Len();
	Size = Size + (FAES::AESBlockSize - (Size % FAES::AESBlockSize));

		Blob = new uint8[Size]; //So once we calculated size we allocating space in memory 
	//which we use for encryption

	TCHAR* KeyTChar = Key.GetCharArray().GetData();            // ...turn key string...
	ANSICHAR* KeyAnsi = (ANSICHAR*)TCHAR_TO_ANSI(KeyTChar); // ...into ANSICHAR array.

//We filling allocated space with string to process
	if (FString::ToBlob(String, Blob, String.Len())) {
		FAES::EncryptData(Blob, Size, KeyAnsi); //We encrypt the data
		String = FString::FromHexBlob(Blob, Size); //now generate hex string of encrypted data
		delete Blob; //deleting allocation for safety
		return String; //and return it
	}
	delete Blob; //deleting allocation for safety
	return ""; //If failed return empty string
}

FString MyClass::Decrypt(FString String, FString Key) {

	if (String.IsEmpty()) return String;  //empty string? do nothing

	uint8* Blob; //we declere uint8 pointer
	uint32 Size; //for size calculation

	//first we need to calculate the size of array, encrypted data will be processed in blocks so
	//data size need to be aligned with block size

	Size = String.Len();
	Size = Size + (FAES::AESBlockSize - (Size % FAES::AESBlockSize));

		Blob = new uint8[Size]; //So once we calculated size we allocating space in memory 
	//which we use for encryption

	TCHAR* KeyTChar = Key.GetCharArray().GetData();            // ...turn key string...
	ANSICHAR* KeyAnsi = (ANSICHAR*)TCHAR_TO_ANSI(KeyTChar); // ...into ANSICHAR array.

//We filling allocated space with string to process
	if (FString::ToHexBlob(String, Blob, String.Len())) {
		FAES::DecryptData(Blob, Size, KeyAnsi); //We decrypt the data
		String = FString::FromBlob(Blob, Size); //now generate string of decrypted data
		delete Blob; //deleting allocation for safety
		return String; //and return it
	}
	delete Blob; //deleting allocation for safety
	return ""; //If failed return empty string
}