You need to activate license in account, so you see the license in middle column (active\running licenses) and license has a key on an info panel.
Then you can activate ZModeler with license key. The best way is to configure online validation
, so ZM can do everything automatically. (this is the only way for older versions)
You can apply license manually (will work for the latest version and the latest build of ZM only) by copying license key in account and pressing Shift key in ZModeler when License Information page is shown. You will see your license key copied automatically and "Verification: Failed" below it; then press "Validate" button in web account to get validation key, copy it too and press Shift in ZModeler again; Verification will change to "Passed today" or "Revalidate in ** days". Press Ok and restart.
Make sure to start ZM as Administrator;
Ensure ZModeler folder is not read-only and, preferable, added to exclude list of your antivirus;
Correct license installation will create "CodeLib.dynamic" file in "Shared" folder of ZModeler. If you see this file, the license is installed in ZModeler (it could be non-validated, it could be expired, but it is installed).