Thank you for your post. My apologies for the delay in getting back to you.
Be default it should be downloaded into your 'Download' folder unless it's been changes on you computer to go somewhere else.
Would you be able to please let me know what browser you're using? There are some browsers that have issues exporting the takeoff data but it should always work on Google Chrome. If you download and install Chrome does it fix the issue you're having? I've put the link to download it below.https://www.google.com.au/chrome/browser/desktop/index.html