Does the QuickBooks Add-In support the Enterprise Edition of QuickBooks?

We haven't tested it directly with that version, but it should support any version that has the ability to import and export IIF files.

Another candid thought on this is that because you are running the Enterprise version of QuickBooks, we assume that you probably have a large number of transactions, customers, or items.... and this would probably not be an ideal fit for the Add-on.  The reason for this is the fact that it uses .IIF files to import and export between the ProductCart database and the QuickBooks data file, and this is something Intuit is no longer encouraging.  Instead, they prefer that the integration is done using their SDK, which is something we hope to provide in the future.  One of the problems this presents, is that it requires components to be installed on the server itself, and most of our customers are running their stores on shared servers (where the hosting provider does not allow 3rd-party components to be installed).