License window don't open

I would like to buy the eM Client Pro license for my personal use. I need it: I have 4 email accounts and the free 30-day trial is expiring.
The Help doc, in section “Main menu and toolbar”, says that the licence can be activated/deactivated thru the Help -> License.
Unfortunately the License menu item does nothing! No license window. How is it supposed to enter registration, after payment?
Tech specs: eM Client 8.2.1478 (856f724), iMac with OS X 10.11.6 (old, but the hardware cannot stand further updates)
Any suggestion?

Solved! After restart of my iMac the problem went away: the license pane is working.
So I purchased the personal license via PayPal, I got the activation key within few seconds, I entered it in the License pane, and I gained the upgrade to Pro.
Sorry for my previous message. Everything is working!