ISO: jiffy corn muffin mix

I have used jiffy corn muffing mix for many years.
Recently, after trying 3 different boxes, the product
failed to raise in my oven. It also didn't taste the same.
After the first time that it failed to raise I thought maybe I had not added the correct amount of milk.
But, as I said, the next 2 boxes failed to raise too. The box I used today I could not find the date where it is supposed to be located so I could check to see if it might be old. Please let me know if you have had any other customers complain about the same problem.

Thank you,
Carol Berry