I got the below error.
Contacting Alteryx help desk did not work (no replay).
Worth double checking if any other version of Alteryx is already installed. If yes, recommend uninstalling. Also check if enough space on C drive
It appears to me that it is more like an internet connection issue.
Maybe your cooperate Proxy is blocking the conenction of Download manager?
Can you try to download the installer directly from
https://alteryx.flexnetoperations.com/flexnet/operationsportal/startPage.do