Problems with encryption and decryption TripleDES in vb.net - vb.net

Question

I'm practicing encryption and decryption with a text file by using TipleDES. I enter a word in a text box, which is in my application, and then click my button that will store the password in the text file. I check the text file to see if it encrypts it which it does and then I try to decrypt the text. It encrypts it again and doesn't decrypt it. I'm not sure what I'm doing wrong.
Public Function EncryptTripleDES(strInput As String, btKey As String) As String
Dim desTDES As New TripleDESCryptoServiceProvider()
Dim hashMD5TDES As New MD5CryptoServiceProvider()
Dim btHash As Byte()
Dim btBuff As Byte()
btHash = hashMD5TDES.ComputeHash(Encoding.UTF8.GetBytes(btKey))
desTDES.Key = btHash
desTDES.Mode = CipherMode.ECB
btBuff = Encoding.UTF8.GetBytes(strInput)
Dim strResult As String = Convert.ToBase64String _
(desTDES.CreateEncryptor().TransformFinalBlock(btBuff, 0,
btBuff.Length))
Return strResult
End Function
Public Function DecryptTripleDES(strInput As String, btKey As String) As String
Dim desTDES As New TripleDESCryptoServiceProvider()
Dim hashMD5TDES As New MD5CryptoServiceProvider()
Dim btHash As Byte()
Dim btBuff As Byte()
btHash = hashMD5TDES.ComputeHash(Encoding.UTF8.GetBytes(btKey))
desTDES.Key = btHash
desTDES.Mode = CipherMode.ECB
btBuff = Convert.FromBase64String(strInput)
Dim strResult As String = Encoding.UTF8.GetString _
(desTDES.CreateDecryptor().TransformFinalBlock(btBuff, 0,
btBuff.Length))
Return strResult
End Function
These are my functions to encrypt and decrypt.
strEncode = EncryptTripleDES(EmailPasswordTextBox.Text, "HTG")
strDecode = DecryptTripleDES(strEncode, "HTG")
Console.WriteLine("Encrypted: {0}", strEncode)
Console.WriteLine("Decrypted: {0}", strDecode)
If I change EmailPasswordTextBox.Text to "This is a Test". It works perfectly. What am I doing wrong?