how to solve your login attempt was not successful please try again login

to make this easy first use static password and user id. read the value of textbox and check using condition :

if(txtUserName.Text=="Abc" && txtPassword.Text=="Abc123")
{
Response.Write("welcome Login"); // code here
}
else
{
//....
}

if it is correct then check your database connection. Using debug check the query that you are passing to database and executing. and wrie code in try catch block and print the exception if there is, from this you can easily find where is the problem.

try
{
//code here...

}
catch(Exception ex)
{
Response.Write(ex.Message);
}

Hope this will help you.
And don't forget to mark as answer if it helps. :)

if(txtUserName.Text=="asd" && txtPassword.Text=="123")
{
Response.Write("Welcome.aspx"); 
}
else
{
your message
or make one label
lblError.text= "PLZ try Again";
}