Licence activation

I have just tried my license to activate but I get the message that I have to deactivate a license elsewhere.
I had, on another computer, eM Client but there is now Linux on it. I have only recently switched to Windows again. Before i killed Windows i did not deactivate anything.
How do I get it activated?

Lizenztyp: NormalWithLifetimeUpdates
Benutzeranzahl: 2
Ausstellungsdatum: 12.01.2018
Ablaufdatum für Support 12.01.2019


You should have de-activated the license before you put Linux on the computer,
but a little late now…

But check the posts here - disregard the title of the link 
The info there will help you…