Most cockatiels LOVE Nutriberries.

you see, the product should be fine but I run into the same problem - they get not so fresh and then birds refuse to eat them. So for me it's a big deal to keep them fresh and slightly soft. First package of avi cakes was a hit, then I bought the second and I could say how drier they were. If my birds wouldn't eat it right when it gotten out of the package, it would get totally dry and they would leave it out.
I still have some sunny orchard nutriberries in a tube that I bought loooong ago. I stopped feeding them when I saw they are not getting eaten.

Storing the food in a small airtight container might be helpful.

Do you keep your in a tube it came in?

I keep it in the original plastic tub. They get used up fairly fast lol.