There is a known bug that can cause playback controls and other menu items to disappear on devices with certain screen resolutions and/or zoom settings.

As a workaround, zooming out with your browser's zoom settings should allow the controls to appear. 

In Chrome, select the View menu at the top of the screen and then select Zoom Out a couple times to see if that reveals the missing menu items. Alternatively, you can choose the 3 vertical dots in the upper right corner and adjust the Zoom settings with the plus or minus buttons.