Do we need a variance/permit to change the use of a current business

We already have a business established on our property for over 15 years, our land is zoned residential but 15 years ago they gave us a permit and variance to run our business. We are looking to change the type of business we are doing and under federal law and state regulations we cannot operate this business from our home. We submitted a variance to our local township zoning board and their lawyer is telling us that we must operate a business from our home on residential land. Although we have had our established business for over 15 years. We are just looking to change the type of business from metal working shop, to distilling spirits. We have contacted the BBT and federal and state laws they told us we cannot operate a business like this from our home, but we already have a business established on our current property. Do we file a variance/permit for just A change of use to the business?