This can be a high impact bug. I have 4 monitors at work and a laptop at home. I now suspect that the configuration at work at the time I shut down Fusion may affect the laptop the next day. Even if I haven't used the laptop in the interim.
I considered that the window might have opened off screen, but mistakenly rejected this explanation, because the laptop doesn't have two screens (and it had been working fine 2 or 3 days ago, and hadn't been used since the last time it did work (e.g., it was not connected to some external monitor)), and because in the task monitor there was no indication of a second window open (something about the type of the window).
I thought I had a corrupted project file ... after a bit of fiddling I discovered that it did it for all projects.
I thought I'd configured the display or windows in some weird way ... Finally figured out how to reset to defaults, nothing.
I thought I had malware ... took a couple of hours to decide that this was unlikely.
I did a simple reinstall ... nothing.
I did a reinstall with manual wiping app-data and roaming ... nothing.
Then I searched for and removed Autodesk stuff from the register file before reinstalling ... nothing.
Then I wondered around the help system with no clear idea what search keywords to try, before finding this thread ... It worked.
Of course, the issue was that it's Christmas and I needed to make a quick fix remotely. So I had no simple way out, like going to the office or calling someone. I was counting on being able to access our designs from my laptop in an emergency. So a 15 min fix turned into 4 or 5 hours of chasing phantom IT problems plus 15 minutes to make the actual fix.