I am new to AECOsim Building Designer SS6, I am facing the same problem which was faced by two other users who posted and got the solution for it.
But in my case, changing text size to even unreadable didn't help. I can't select any floor using floor selector. Already gone through two threads available in this forum and tried everything possible. Please help.
Change the mouse double click settings to the slowest, this should solve the issueAECOsim has a faster double click response than the windows settings, with the medium speed of the windows settings most users can't do it in AECOsimI had the same issue as you, I tried this solution and it's working fine now