Make sure you have pop-ups enabled. Here's how
Do you have pop-ups enabled in your browser? The file that is generated opens as a pop-up in a new tab, that's why you need to have pop-ups enabled.
Turn pop-ups On on Chrome
On your computer, open Chrome.
At the top right, click More. Settings.
Under "Privacy and security," click Site settings.
Click Pop-ups and redirects.
At the top, turn the setting to Allowed.
Something else you may want to check if you cannot download is that the files that you are uploading should be 32 bit and not 16 bit (this can cause issues with downloading). You can use a converter like this one to convert your files before you upload them to the interior generator:
Larger files (100+ pages) might take up to a few minutes to compile