You are using the same control (
textBox2
) for the user id and password.
Could it be possible that you failed using the right textbox for the password?
As a side note, you should take the habit to rename your controls and give them meaningful names. This would allow you to spot such mistakes very quickly. Compare to:
connectionString = $"Data Source = {tbDataSource.Text}; UserId = {tbUserId.Text}; Password = {tbPassword.Text}"