there may be a php error preventing the redirect, add the following code at line 1:
to show any php errors.
On the cart display page, when you run the checkout wizard it will automatically update to send the checkout button to the checkout page. if this redirect is not working, add the error reporting code to see if the issue is caused by a php error.
if you need further assistance, send a copy of the page so i can see the code and a link where i can investigate.