I did a fresh, clean install of LabView 2018 and NI-VISA 18.5. Then I run NI-MAX, and I see the error in the screenshot complaining that C:\Windows\System32\visa32.dll is missing.
Of course, the file is there, it's just that the error message is misleading. A little messing around with dumpbin reveals that nimax.exe is a 32-bit executable (I suppose the giveaway was that it was located under C:\Program Files (x86)\), and despite the name, C:\Windows\System32\visa32.dll is a 64-bit DLL. In fact, (believe it or not), the 32-bit compatibility DLLs are supposed to live under C:\Windows\SysWOW64\. That's right, the 64-bit DLLs are under System32 and the 32-bit DLLs are under SysWOW64. As if multilib weren't complicated enough already.
So, my question is, is there any way to coerce the NI-VISA (version 18.5) installer to install the 32-bit libraries in parallel, so that NI-MAX works? I really like that tool.