I was told that there was an internal error after I inserted the free serial or existing commercial serial when the demo expired in my Win10 
Please advice any solution, thanks for help!
Hello Ken,
are you sure you are copying the license key correctly?
I see 2 PRO licenses and 1 FREE under your email address. The FREE one isn’t activated. Is it the one you’re trying to use?
Please contact me at rust@emclient.com with a link to this forum topic if trying to copy the key again does not work.
Regards,
Olivia