Problem:

I can't use the software. It gives Error 5013 even if I've already used my license to activate previously.

Solution:

Please try these:
1. Turn OFF your anti virus program and start OptiSurface Designer and see if that solves it.
2. If you're using company internet, try using an internet connection that doesn't have a company firewall e.g. use a mobile phone hot spot or a wifi hot spot away from the workplace.