Check the abandoned/live carts to see if there is a high number of customers leaving the site before checkout.
Check their smarter stats page to see if they are experiencing a decline in traffic.
Run a test order to be sure that there isn't anything preventing customers from checking out.
All of the above
Process payments through a payment gateway rather than through PayPal
Add SEO tags for all product pages
Optimize the images on their website to reduce the amount of data which loads on each page
Change their domain name to a shorter name
Endicia can only process orders from Volusion which have their order status marked as “Ready to Ship”.
Endicia can only process orders with product weights over 13 oz.
Endicia only processes orders given a valid USPS shipping method and service code.
The Volusion store must have at least one, valid USPS shipping method made active in the Volusion Administration Page.