I have entered the product key for the ENv11 CD supplied by work for a multi license product - it has not been recognized

First you have check multi license pack is for only five or some number of copies you can install from that cd and update it. The multi license pack is for only five or ten copies of the orginal cd. Please refer cd where you bought. The problem occurs is when you install the software more than that you buy multi license pack ok. please see the license .