Votes not opening automatically when you show a voting question is usually caused by auto launch votes not being switched on or by there already being voting data present on the slide.
Are you showing the slides full screen in presentation mode? If not, votes will not launch. Go to Slide Show and click on From Beginning or From Current Slide to put the presentation into the correct mode.
Does your voting slide already show results / a graph?
If so, you will need to clear the data to reset the presentation.
Click here to learn how to clear the voting data
If there are no results on the slide, try pressing V on your keyboard. Does that launch the vote? Pressing V on each voting slide will trigger the voting activity.
There is also a global setting which will trigger each vote automatically. Escape out of slideshow mode and go to Add-ins > CLiKAPAD and look for the Auto launch votes option. If there is no tick next to that, you will need to press V each time you reach a voting slide. Just click on the Auto launch item in the menu to switch this automatic trigger on. Next time you view that menu, you will see it has a tick by it.