It's not a firewall issue. I've never had this issue before and a lot of people are having the same problem. .
There are just you and another user posting here. We have thousands of customers, and every day lots of users activates or deactivate the software. The The Esellerate activation server is up:
http://activate.esellerate.netWe haven't got any notification from Esellerate about a possible downtime, and nobody else has reported problems with activations today, except the two reports here. I've checked all the successful activations made today, and there are plenty.
If it's not a firewall issue, maybe it's a permission issue, try to run FSX As Administrator.
Another possible issue, you have installed another product from another company that use Esellerate, but that comes with a wrong/older version of the library. We obviously supply the correct and latest version of it, but we had reports of other products installing older versions, that might cause a conflict. In this case, search your system for the following files:
C:\Windows\Esellerateengine.dll
YOURFSXFolder\Esellerateengine.dll
C:\ProgramData\Esellerate\Esellerateengine.dll
Remove ALL the instances of the .dll, especially if you find one in C:\Windows, then reinstall GSX, which will restore the correct one, in the correct place, which is C:\ProgramData\Esellerate\