You need to allow the applications tekla.exe and lmgrd.exe to operate through the firewall on the license server computer to enable licensing traffic. The instructions apply to Windows Server 2008.
To allow exceptions for lmgrd.exe and tekla.exe :
If you have selected the check box, the modifications do not take effect.
By default, the path is ...\TeklaStructures\License\Server.
The lmgrd.exe application is added to the list of exceptions.