Rsa decription with same key pair doesn't work

Question

I am working on a cryptographic app in C# with .NET Framework. One of it's functions is to let the user store an (or multiple) RSA asymmetric key pair in the Windows KSP, export the public key to a BLOB and decrypt messages (in fact, it will use RSA only to encrypt/decrypt a symmetric key) encrypted with that one specific key. I am using the CNG implementation in the System.Security.Cryptography namespace.

In order to test it's functionality, I have created a keypair and given it a name. After that, I have exported the key using the following function:

public static byte[] GetPublicKeyBlob(string keyContainerName)
            {
                try 
                {
                    if (!CngKey.Exists(keyContainerName))
                        throw new CryptographicException($"The Key Service Provider does not contain a key with the name: '{keyContainerName}'");
                    cngKey = CngKey.Open(keyContainerName);
                    rsa = new RSACng(cngKey) { KeySize = keySize };
                    return rsa.Key.Export(CngKeyBlobFormat.GenericPublicBlob);
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return null;
                }
            {

The (static) fields are the following:

public static RSACng rsa;
public static CngKey cngKey;
public static int keySize = 2048;                                                           // used
public static RSAEncryptionPadding rsaEncryptionPadding = RSAEncryptionPadding.OaepSHA512;  // later

Next, I used the following function to encrypt some sample data:

public static byte[] Encrypt(byte[] input, byte[] key)
            {
                byte[] output = null;
                try
                {
                    cngKey = CngKey.Import(key, CngKeyBlobFormat.GenericPublicBlob);
                    rsa = new RSACng(cngKey) { KeySize = keySize };

                    if (input != null) 
                        output = rsa.Encrypt(input, rsaEncryptionPadding);
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                return output;
            }

I took the output (which looked like a normal output for a cryptographic function) and used it as an input for the Decrypt function:

public static byte[] Decrypt(byte[] input, string keyContainerName)
            {
                byte[] output = null;
                try
                {
                    if (!CngKey.Exists(keyContainerName))
                        throw new CryptographicException($"The Key Service Provider does not contain a key with the name '{keyContainerName}'");

                    cngKey = CngKey.Open(keyContainerName);
                    rsa = new RSACng(cngKey) { KeySize = keySize };

                    if(input != null)
                        output = rsa.Decrypt(input, rsaEncryptionPadding);
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                return output;
            }

Here, rsa.Decrypt(input, rsaEncryptionPadding) threw an exception with the message: "The parameter is incorrect.".
I wrote another Encrypt function using the saved key itself, as it follows:

public static byte[] Encrypt(byte[] input, string publicKeyContainerName, bool setCngKey = true)
            {
                byte[] output = null;
                try
                {
                    if (setCngKey)
                    {
                        if (!CngKey.Exists(publicKeyContainerName))
                            throw new CryptographicException($"The Key Service Provider does not contain a key with the name: '{publicKeyContainerName}'");

                        cngKey = CngKey.Open(publicKeyContainerName);
                    }
                    rsa = new RSACng(cngKey) { KeySize = keySize };

                    if (input != null) 
                        output = rsa.Encrypt(input, rsaEncryptionPadding);
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                return output;
            }

The same function for decryption was used with the same result.

At this moment I am stuck and I do not know what to do to solve this problem. What am I doing wrong?