Hi @KNIME_JK, welcome to the KNIME forum.
It looks like you are on a corporate network and your company has a proxy server that is blocking access to the KNIME update site. Are you able to contact your network administrators to ask them if access can be granted?
The alternative, if you are able to get access to the update files by other means is to download the update files and then perform an offline update.
Better though if you can persuade somebody to allow access!