[someone@somewhere app]$ sencha upgrade
Sencha Cmd v7.2.0.56
[INF] Determining the latest version of Sencha Cmd
[INF] Downloading : ....................
[INF] The latest version of Sencha Cmd is
[INF] Downloading SenchaCmd- from http://cdn.sencha.com/cmd/ to temp folder /tmp/sencha1588077104046
[INF] Cleaning up temporary files in /tmp/sencha1588077104046
[ERR] Error downloading http://cdn.sencha.com/cmd/

Looks like someone bumped the version without providing the linux binary - I was able to download the windows version though.