FWIW - At 10.6.1 and upgrading to 10.8.1 I was presented with this message as well. I was able to click "Retry" and it kept on going. The entire portal.exe upgrade process took almost 3 hours.
this is happenig the same with me. Im trying to install Portal for ArcGIS 10.7.1, and during the install it gives me an error "Installer No longer responding". Anyone knows the solution for this ? thanks?
Update. I just hit the "Retry" button and it chugged along. Took a while, but it progressed. I would recommend however, that a VM snapshot is done on that machine before the installation ever begins in case the registry or otherwise becomes corrupted for some reason or another. Then try a fresh install again.