Trying to check for XCTU updates using Help->Check for XCTU Updates gives the following message
Unable to connect to repository ftp://ftp1.digi.com/support/XCTU-NG/java_18/repository/content.xml
Connection refused: connect
Could it be that you are behind a firewall or using a Proxy Server? You may need to have your IT admin add the ftp1.digi.com to your exclusion list on your Firewall.