Customers can not advance into checkout phase

When a customer adds a product to their cart, if they click proceed to checkout, it does not proceed and just loops them back to their cart.

Please help?!

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Zen Cart v1.3.9c/v1.3.9c

The issue started when we tried to export some products into a new website.

It just continuously loops customers to their cart and cannot advance to checkout.

Dugouthats.com

The issue started when we tried to export some products into a new website
Did you backup your DB before doing this??
If not you should have as a matter of procedure

kobra:

Did you backup your DB before doing this??
If not you should have as a matter of procedure

We keep getting the following error messages on our server:

The following guide from our KnowledgeBase will show you how to find your access logs and error

http://kb.mediatemple.net/questions/732/Where+are+the+access_log+and+error_log+files+for+my+server%3F#dv_40

I wish there was more I could do to assist you, but I hope this helped you out and I'll definitely answer any other questions you may have. Just let us know!

Thedugout:

The issue started when we tried to export some products into a new website.

Sooner or later you may find that one of us will come back to this for a few more details, but meanwhile, I've visited your store and have determined that the checkout button link is pointing to:

http://dugouthats.com/shop/index.php?main_page=shopping_cart

It should be pointing to

http://dugouthats.com/shop/index.php?main_page=checkout_shipping

This is what is causing the loop.

So the question now is How/Why is this link incorrect?
The link is dynamically created using information from data stored in the /includes/filenames.php file.
Typically this file isn't something that most people will need to modify, but nonetheless it is worth checking.

Here is the relevant portion of what an unmodified filenames.php includes:

define('FILENAME_CHECKOUT_CONFIRMATION', 'checkout_confirmation');
define('FILENAME_CHECKOUT_PAYMENT', 'checkout_payment');
define('FILENAME_CHECKOUT_PAYMENT_ADDRESS', 'checkout_payment_address');
define('FILENAME_CHECKOUT_PROCESS', 'checkout_process');
define('FILENAME_CHECKOUT_SHIPPING', 'checkout_shipping');
define('FILENAME_CHECKOUT_SHIPPING_ADDRESS', 'checkout_shipping_address');
define('FILENAME_CHECKOUT_SUCCESS', 'checkout_success');

How does this compare to your file (in particular
define('FILENAME_CHECKOUT_SHIPPING', 'checkout_shipping');

If you find your file contains valid data as above, the problem will then point back towards your template files, which has probably
got something hardcoded and/or possibly somehow ignoring these defines.
A quick/simple test/check for this is to temporarily revert back to the 'classic' template to see if the problem goes away.

Let us know your findings because this could be a dead end or red herring..
A whole lot actually depends on what you mean when you said you 'tried to export products into a new website'

Cheers
Rod