Make sure the computer is connected to the Internet.
Close the installer of Expert PDF and temporarily disable all protection software that may prevent the software from establishing connection with the remote server.
If the host computer uses proxy settings to connect to the Internet, please use Advanced Options to configure Expert PDF installer gets through the proxy settings:
Press Proxy Settings:
Either enter proxy server details manually or press Get Proxy Settings to copy the Proxy server record in Internet Options > LAN settings
then proceed to the next step and complete the download of components.
This should help the software to install successfully.