If you want to use the latest version of DbVisualizer Pro and any of the following apply you need to renew your license:

Open Help->About. If Version is 3.*, you need to renew.

Open Help->About. If Version is 4.*, you need to renew.

Open Help->About. If your Upgrade Expiration date has past, a message is displayed.

You may decide to stay with the version you are currently using. Old versions are available for download.