When you first launch the Trial version of ExtendSim, you have 30 days to try it out. Once you reach the end of that month – if you haven’t already purchased the product – that free Trial period will end. All the model files and blocks you created during the Trial period will still be yours, but ExtendSim will no longer launch on your system.
If you try to download and install another Trial version to get another 30 days, it won't work. Your system will only allow one free trial period.