Padding is invalid and cannot be removed aes

Question

I have searched solutions on this website but none solved my problem. Sometimes I recieve "padding is invalid and cannot be removed" exception. I don't know what to do. When I tried some solutions, there was empty decrypted text or it didn't work. Here's my class

static class Aes
{
    public static string bytesToHexString(byte[] key)
    {
        return BitConverter.ToString(key).Replace("-", String.Empty);
    }

    public static byte[] stringToBytes(string key)
    {
        return Enumerable.Range(0, key.Length)
                 .Where(x => x % 2 == 0)
                 .Select(x => Convert.ToByte(key.Substring(x, 2), 16))
                 .ToArray();
    }

    public static void generateKeyAndIv(out byte[] key, out byte[] IV)
    {
        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
        {
            aesAlg.BlockSize = 128;
            aesAlg.KeySize = 256;
            aesAlg.Padding = PaddingMode.PKCS7;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.GenerateKey();
            aesAlg.GenerateIV();
            key = aesAlg.Key;
            IV = aesAlg.IV;
        }
    }
    public static string EncryptStringToString(string plainText, byte[] Key, byte[] IV)
    {
        byte[] bytes =EncryptStringToBytes_Aes(plainText, Key, IV);
        return Convert.ToBase64String(bytes);
        //return Encoding.UTF8.GetString(bytes, 0, bytes.Length);
    }

    public static string DecryptStringToString(string cipherText, byte[] Key, byte[] IV)
    {
        //byte[] bytes = Encoding.UTF8.GetBytes(cipherText);
        byte[] bytes = Convert.FromBase64String(cipherText);
        return DecryptStringFromBytes_Aes(bytes, Key, IV);
    }

    public static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key, byte[] IV)
    {
        // Check arguments. 
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("Key");
        byte[] encrypted;
        // Create an AesCryptoServiceProvider object 
        // with the specified key and IV. 
        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
        {
            aesAlg.BlockSize = 128;
            aesAlg.KeySize = 256;
            aesAlg.Padding = PaddingMode.PKCS7;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            // Create a decrytor to perform the stream transform.
            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);


            // Create the streams used for encryption. 
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    }
                }

                encrypted = msEncrypt.ToArray();
            }
           /* using (var msEncrypt = new MemoryStream())
            using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
            using (var swEncrypt = new StreamWriter(csEncrypt))
            {
                swEncrypt.Write(plainText);
                csEncrypt.FlushFinalBlock();
                encrypted = msEncrypt.ToArray();
            }*/
        }


        // Return the encrypted bytes from the memory stream. 
        return encrypted;

    }

    public static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)
    {
        // Check arguments. 
        if (cipherText == null || cipherText.Length <= 0)
            throw new ArgumentNullException("cipherText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV");

        // Declare the string used to hold 
        // the decrypted text. 
        string plaintext = null;

        // Create an AesCryptoServiceProvider object 
        // with the specified key and IV. 
        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
        {
            aesAlg.BlockSize = 128;
            aesAlg.KeySize = 256;
            aesAlg.Padding = PaddingMode.PKCS7;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            // Create a decrytor to perform the stream transform.
            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

            // Create the streams used for decryption. 
            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {

                        // Read the decrypted bytes from the decrypting stream 
                        // and place them in a string.
                        plaintext = srDecrypt.ReadToEnd();
                    }
                }
            }

        }

        return plaintext;

    }
}

Please help because I'm exhausted by finding solution on my own