I too am using multiple monitors and VST Connect PRO v 4.0.42 (and Win10 Pro) but I noticed a slightly different behavior/issue. VST Connect PRO paints up just fine on both monitors when I use the menu to select VST Cloud>VST Connect PRO>Open VST Connect editor.
However, when I use an assigned Key Command to “Open VST Connect editor” it only paints up correctly if the VST Connect editor was last closed on my main (left) screen. If it was last closed while it was on my right screen, it fails to paint up correctly and instead only shows a black window.
So, using a Key Command as opposed to the N10 menu system results in two different behaviors.
I hope this helps you to further diagnose the issue.