you won't be able to add the checkout button to the template. this is a limitation to templates and how they work.
the checkout button uses server side code in the head of the page to do the redirect to the checkout page. templates won't work with server side code in the head.
The work around to this is to use the Data Bridge framework Builder tool to convert template to a Theme and use the Framework themes on the page:
There are a few different things that can cause the cart to remain empty after adding an item, first make sure you aren't switching domains when going from the add to cart page to the view cart page. what i mean by this is changing from the www address to the non www address or vice versa, for example, adding to cart at:
and them viewing the cart with the address not using www:
the www versus non www adresses are separate domains, and separate session.
The next thing to check is that the eCart add to cart page uses the same eCart object as the view cart page.
next is to check the server is capable of saving sessions. use the attached sessionTest page to make sure sessions are working. if the session test fails, you will need to contact the host to have them fix the problem, most likely a bad session.save_path setting in the php.ini file.
to start all over again, delate the WA_eCart folder and recreate the add to cart and view caret pages.