Did you put in the serial number?
The serial is in your account under My Serial Numbers.
Find GenX in DS4.5 Help->About Installed Plugins. Scroll down to GenX, there should be a long box to paste in the serial number.
After you restart DS4.5, GenX should show up in Windows>Panes>GenX.
If it doesn’t, go to Edit / Customize and look under “Panes” on the left side.