I just bought a new pen for my Microsoft Surface Pro 3; a Bamboo Ink Pen. It similarly works the same way as the Surface pen (but comfier for me) with the bluetooth technology. I had issues before with my Surface Pen and Clip Studio Paint with the pen pressure, but I only needed to restart my Surface until Pen pressure was working again.
But it is not the case with my Bamboo Ink Pen.
The pen pressure is working perfectly with Windows Ink, Bamboo Paper, Photoshop, but not Clip Studio Paint.
I tried a lot of different things, like switching from Wintab to Pc Tablet, restart the wacom professionnal services, reinstall the Wintab driver, switching to tablet mode, etc.
I also tried a lot of different brush and adjust the pen pressure within Clip Studio Paint, but nothing seems to be working.
Its kinda of a shame, because I really like to use Clip Studio Paint to draw versus Photoshop. I'm also wondering if the iPad app would be available someday to windows tablets.