despite the cool interface, yeah , that software is terrible.
now keep in mind that pro2 usb driver does not support multiclient midi on windows 10, multiclient miidi simply means that you can use it on multiple applications at the same time.
As for cubase check if any of the midi ports are active or if the midi clock for the pro 2 is active and disable it, any port usb midi port shared within cubase will make the editor unavailable.
TBH this is an issue with almost any synth connected through a usb.
That said as a pro 2 vst editor i suggest you the codeknobs one, the soundtower one has an awful bug and they never fixed, the filters envelope are not bipolar, they just send positive values and they're offset. Simply said is impossible to make sweeping tones unless you creat a dc modulation on the filter envelopes