I'm having the exact issue- I can successfully install Fusion when I set up another user on my Mac but not on my main account. I have been through all suggestions on this board and nothing seems to work. I have deleted the Autodesk folder, given it all the various permissions I can give it and it still comes back with the error "Access to install directories failed". This seems like a bug on the Autodesk side, as I have never had this issue with any other software- and I have been trying to do an install on this machine periodically over the past couple of years, thinking Autodesk would get enough complaints and finally look into and fix this issue.
BTW, it is the education version I am trying to install.
Any help would be greatly appreciated as this is extremely frustrating.
TIA