accessibility – NVDA unable to review landmarks on a webpage

I have to fix up a website to make it more accessible. Someone said my webpage is missing the main landmark. To confirm this, he said to download NVDA software, open up the NVDA software, then navigate to my website, then press Insert F7 to open up the Elements List which should look like this:

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But when I press Insert F7, my browser gives me this pop up instead:

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Does anyone know how to use NVDA to open up elements list to reveal my landmarks?