Custom form not being recognized as preferred on separate site?

We're currently in the process of updating to SuiteCommerce Advanced have been running some test orders through the new testing site to get things setup.

In the past, we set up a custom sales order form to apply to all sales orders that come through our site. However, the orders that we've placed through the testing site aren't using the preferred sales order form, are defaulting to the standard sales order form and confusing our sales staff. All other sales that come through our current live site using the correct form.

Is there some reason that this would be happening? I've double-checked that it's the preferred from, adding it as the preferred form to the sales staff's user role and even disabling the standard form at the sales staff's user role level. All to no affect.