Can't get ShowControl 2021 working with ShowNet interface

OK, if you did not buy a license it cannot work, of course!
The ShowNET interface is the Digital-Analog-Converter (it can do a lot more, but for the use with software this is the feature we need). It has a built in License for the full version of Showeditor. Showcontroller is a professional laser control software that is totally independent of Showeditor and also has different control logics (drag and drop programming, etc.). You need to buy a separate license if you want to use it (which is really low priced btw). It uses the same hardware as Showeditor: the ShowNET interface (as external device) or as internal mainboard (as in most Laserworld, tarm and RTI laser systems) can be used by various control software.
So for using Showcontroller with your ShowNET, you just need to get a license. https://www.laserworld.com/en/laser-software/showcontroller-license

Did you insert the Shocontroller license dongle? It's the red USB device, looks like a USB stick. You received it when you bought the license (look at the pictures here, they show it: https://www.laserworld.com/en/laser-software/showcontroller-license)
If it's inserted, but does not work either, please check if the red LED is on at the USB dongle. If not, it may help to give the computer internet access once (just so the USB dongle can be detected, not needed later on).

Also, if you have a full license, but you have installed the Demo-Version of Showcontroller before, please completely uninstall this Demo version and do a clean full version installation of the software.