Steve,
I have seen this sort of thing before when the PSI/Upgrade tool can't see the running installation of Apache due to it being an SSL configuration (although this would be on an existing system, not a new install) - ie Apache is running on SSL port 443 and the PSI is trying to access it on port 80 or vice versa.
I know of no way to do an SSL install of Apache via the PSI at versions up to and including 10.1, but I have never installed 10.2 - presumably this is now not an option at install time in the PSI? If it is now possible to configure https out of the box on installation (I somehow doubt it), then this would be somewhere to look...
Also, are you using standard port 80 for your Apache install, if not there may be some confusion arising as to where the PSI is looking to find your Apache Server?
Do you see an entry in the Apache access logs for when the PSI tries to detect if Apache is running at the part of the install just before it exits - presumably if the PSI is actually able to test access to Apache, you should see something in the Apache logs? This might give you a clue as to where to look.
Rgds
Gary