Here are some possible reasons.
1. Check DemoCreator version that you purchased.
Note: Perpetual license users of DemoCreator need to pay for the upgrade to higher versions. For example, version 4 perpetual users can activate and use version 4 but it would become free trial plan if they use version 5.
2. Check if you have logged in DemoCreator software.
3. Check expire date of your subscription plan.
4. Check if you have purchased the correct platform.