I protect my app with 30-day evaluation period. But I get the error message "License is required" when testing the app.
You probably have a Key already created on the machine that is also expired. When you click the "Register later" button, the system finds the expired license. So it shows the message "License is required". Note that if there is the same Key (e.g. same type, Program ID) on the machine, the system will not overwrite the exiting Key.
Please use the Key Inspector tool to destroy All Keys. So you don't get confused from any existing Keys on the machine. When you start the protected program again, refresh the Inspector. You will see a new Key created. The behaviors should be as expected. You can observe and track the properties such as Max-Day in your tests.
We suggest that you try again. Starting by using ElecKey Integrator to protect a program with Local Key first. Remember to use the Inspector to destroy All Keys before starting the next test, e.g. using the API.