ProVide has replaced zFTPServer, and its not possible to upgrade to ProVide from zFTPServer through the administration tool or Web GUI.
To upgrade to ProVide use the following steps. (Make sure you have an active license)
1. Make a copy of your existing zFTPServer folder, just to be extra safe.
2. Download ProVide from provideserver.com
3. Run the setup and click yes that you want to upgrade.
4. If you do not create any admin account, you will use the one you had in zFTPServer. If you do not make any change to the certificate during setup, it will use the one you had in zFTP.
5. Uninstall zFTPServer, then you are ready to continue use ProVide just as zFTPServer (Web GUI version)