PollDaddy plugin – embedded pop-up survey, but page menu bar lays on top

Hi everyone, my site is https://supermarketsafety.net/survey. My question is the about the “Poll Daddy” plugin. I’ve installed the plugin, created a survey, and followed the instructions to embed a few lines of javascript HTML code into the page where I wanted the survey window to “pop up” on top of the page contents.

The problem is that now, the page menu bar shows up on top of the survey pop-up window – which is distracting and weird-looking. PollDaddy Support says the code that is creating the menu bar originates from the website, so the problem needs to be solved in CSS/WordPress.

Has anyone encountered a similar problem, or have ideas on how to fix this? Thanks very much.