Just (after much agony) upgraded Windows to 64 Bit (in Parallels on a Mac). Windows environment appears to be working.
Installed Xojo 2018.4. Copies Plugins from Mac installation.
Start Xojo. It goes through all its startup checking and then just disappears. No error message; no dialog.
Does it run without the plugins?
Grab https://docs.microsoft.com/en-us/sysinternals/downloads/debugview and run it before running Xojo to see if anything obvious jump out at you.
Failing that, try grabbing the plugins again from the authors.
It was something about plugins. I put back only those I knew I was using in the project I need to work on. Xojo has started up, and the project (copied from the Mac) compiled successfully.
My bet (more research is needed) is that Xojo Windows does not know what to do with Mac-only plugins. I’ll report back when I know more.
Thanks for the tip.