When I'm working with Copernicus, I don't see any changes in the viewport while I'm moving any parameter slider. It waits until I release the mouse button then I can see the result in the viewport. I've seen videos showing realtime update while changing parameter values. Does anyone knows what's happening? It happens in Scene View and also in Composite View.

Maybe you changed cooking update mode to "On Mouse Up" and forgot about it? Still happens to me occasionally.
https://www.sidefx.com/docs/houdini/basics/cooking.html#update-menu [www.sidefx.com]

LOL That's it! I always use Auto Update or Manual, not used to this behavior. Thank you so much!!