[HCHSP] Market Magnate: Can't 'Convince to Buy' during Food Sale

The “Convince customers to buy something five times during a food sale” task from the Market Magnate aspiration will not complete.  My sim has maxed cooking & charisma skills, but the “convince to buy” interaction is never successful.  I have tried using different foods, setting different prices, and selling at different locations, but nothing seems to work.  The task is still at 0/5.  I play on PC & I have never used mods.

Edit By crinrict: Adjusted Title