1.20.1, Create 0.5.1.j, Create cobblestone 1.4.2 (though I was having this issue with prior versions of Create and CCobble as well). This issue occurs with the mod's default config:

Generators don't produce cobble. Getting this in the log whenever I place or interact with one:
[02:19:18] [Render thread/INFO] [Create cobblestone/]: Trying to update generator type from "none" to "none"
[02:19:18] [Render thread/INFO] [Create cobblestone/]: Changing generator type from "none" to "none"

I assume something's gotten confused in the backend.

Please send the full log and a screenshot/video of you placing the generator

Never mind, I figured it out! Turns out I'm just stupid and didn't realize you had to right-click on the generator with a cobblestone (or other) block to get it going. Sorry!