When adding users to the proxy database, I cannot see previously created users.

Make sure the proxy is at 2.10a software/firmware level or newer. If not, you can download that version from our web site at:
http://www.multitech.com/en_US/SUPPORT/Families/ProxyServer/firmware. If the proxy is at that version, downloading the firmware and default configuration will put the device back to factory settings. After adding a user, there is a download button that needs to be clicked on. That will save your entries.