Where to start...
To soften the cookies, the plastic bag was a good idea. Take a sheet of paper towel, wet it, then wring it out, form it into a ball, and add to the plastic bag. Seal tight. The cookies will absorb the moisture from the towel.
To avoid this in the future:
Maybe your oven is hot, or the recipe temperature suggestion is too high. Reduce it.
Maybe the cookies tray is too thin, in which case use a silicon mat on top.
Hard cookies may not have enough fat.
Maybe it was rolled too thin. That would dry them out.
They might be too dense with insufficient liquid.
As you can see, there are any number of variables to adjust.
Atlantic Time (AT)