Using Acid 8 pro ( ver8.0.10) build 20 64 bit with windows 10. Its been working fine. all of a sudden the Fx button when clicked does not open the plug in window. I've uninstalled and re installed 2x and even went back to last weeks windows config.
you could also try to open the plugin window via menu bar using View/Audio Plug-in. We had also an issue that the plugin window opens really small. The you will just see the "x" for closing the window. May be you check if this happens and then resize the window with the mouse. Please let me know if this helps with your problem.