. Cause default Scroll function is not working here? 
@icqe
Option 1. Press f2 on your keyboard to enable manual control (afterwards use F1 to go back to normal).
Option 2. click the icon shown in the picture below and choose browser control type.
0_1572704069582_0a63732a-d14d-4764-8f4c-7d2c3913315b-image.png