You can see if you have sessions waiting to be uploaded or not. To do this, go into the Simulator and click on Settings, at the top. At the bottom of the menu you will see "About the App". Click on that menu and see if the number in "Sessions waiting to be uploaded" is zero or not.
If it's zero, the session has been successfully uploaded to the website, though it may not have been processed yet. It will appear in your history in a few hours.
If the number is not zero, the firewall or antivirus on your computer could be hampering communications between the Simulator and the server. Try adding an exception in both tools for our program (BSim2.exe), or temporarily disable them. If the antivirus is free, you can simply uninstall it and install a different one later.