why is it saying I don't have alicense

I have been using em client for several years.  It is on a single desk top and I have two email accounts: henrywisniewski@frontier.com and thenyskis@frontier.com. I have been operating in this under the free license. Suddenly, the em client puts me offline and tells me I do not have a valid license.   WHY???

If you go to Menu > Help > License you should be able to activate the license.

But this could be because you activated the license on another computer, in which case you want to deactivate it on the other computer first as the Free License can only be used on one computer. It could also happen if the motherboard was changed in your computer as the license server will assume that this is a different computer.