Best contact for Market Press questions

We're having a shipping error code from FedEx that recently appeared. FedEx tech support suggests the problem is on the site as all is well on their end.
Question is: who and how is the best and fastest way to work with someone to correct this issue to customers can complete an order?
FedEx tech support welcomes calls from vendors, but I'm assuming this may not be an option for Market Press?
This is probably a very easy fix as it most likely is pointing to a wrong or expired IP address, however we don't know how to correct this. The error code is showing as an "internal error".
Please let me know who is best at Market Press to correct this situation. Thank you.