Persistent error messsage saying eM Client does not have a valid licence - but it does

I converted my Windows Live Mail over to eM Client a short time ago due to never-ending error messages on Live Mail.
I now have eM Client on two PCs in my home (used for different purposes) and, so far, I have been very pleased with it but it is now starting to give me the same problem I had with Windows Live Mail - persistent error messages.
The error message that keeps coming up is that eM Client does not have a valid licence - but I know that it does because I had to put in the activation key for the free version that I chose. Now, I have to keep reactivating it every time I get this message (on both machines).
The only other annoyance is that an earlier version of eM Client installed about a year ago (but still 7.2) does not show the Contacts notice at the bottom of the side bar under Calendar and Tasks.  It shows this perfectly in the slightly later version that I installed this year.  
Otherwise, eM Client works very well.
(I still use Windows 7 (64 bit) on both  wi-fi networked machines.) .
Can you help?

Hi George,

Do you have two FREE licences in order to activate on two machines? The FREE licence has this limitation but you an register for another FREE licence at: with an unique email address.