That sounds like a really strange problem!
I've had occasional hiccups with S1 at that point in the startup process, hanging on "MIDI engine reset requested" or some message similar to that.
I'm on a Mac myself, but what I've done to fix this is to remove the application support files ending in .settings from my user account's ~/Library/Application Support/PreSonus Software/Studio One 4 folder on a Mac, but I think these files reside in:
C:\Users<username>\AppData\Roaming\PreSonus\Studio One 4 on Windows. Try deleting the "x64" folder from there and restart S1.
If that doesn't work I've gone on deleting the remoteservice.settings file and other files and tried starting the application repeatedly until it works... No silver bullet, but might do the trick.
These files store files regarding your user preferences, so they will be re-generated when you start the application if they're missing.
Some preferences must be set up again if you've changed the defaults.