Hi chandan sahni,
I am also facing the same issue. For Okay and Cancel button I found a shortcut ,you can use the shortcut CTRL + ENTER for the options that you can view & edit. This shortcut works to click "OK" everywhere in studio pro.
Hope it will help you.
Can you check your project user roles tab, whether you added the user roles or not. If no means please add the user roles then try It.
Thanks & Regards