I downloaded Office for Mac from the Office365 software download page. When prompted to activate against my Office365 account, I entered my details.
Initial attempts to activate failed, claiming that my username/password was incorrect. Guessing that Office for Mac was getting confused because I've enabled 2-factor auth on my O36 Microsoft ID, I created an app password and entered that instead.
However, Office is now claiming that "The account isn't associated with this Office product".
I checked my Office365 settings and I still have 2 Office activations available!
I then tried installing the new Outlook client. While it had more smarts about my 2-factor authentication requirements, it too claims I don't have an Office365 subscription, despite that clearly not being the case:
FWIW, I am attempting to install Office on a Mac that I have just clean-installed OS X Yosemite on a freshly reformatted SSD, and there's nothing else installed on this machine at present, other than the apps etc. installed by default on OSX.