Hello Loupa,
Do you have the same issue with other customers in Connecticut?
I would try to narrow the issue to
a) The product
b) The company
c) The state
Check the customer's GeoCode and TDM. Just couple ideas - you didn't assign a GeoCode to the customer or your TDM record has a time limit, which just expired or you sold your product using a wrong company/division (TDM exceptions are based on a company/division).
In first case you can fix with R730101; in second case you need to use TDM; in third case there is an error/mistyping in the Sales Order application.
Good luck!
Alex