My next arrows don't show up again when I accidentally skip a forced question

So I wanted to get rid of previous and next arrows for some questions by putting in this code #PreviousButton, #NextButton{
display: none;
}
in "Add custom Css" option
Then for the questions I wanted the next arrows for, I put in the javascript code jQuery("#NextButton").show(); in the js(OnReady) of each question. However, all of my questions are forced. When I accidentally clicked on the next arrow without completing the question, the next arrow completely disappeared and won't come back. Is there a way to fix this? I'm not sure what's happening. Thank you!