This happens from time to time due to the way the package downloads .html files.
To fix it, find your downloaded .htm files either in the package executor window (right click URL -> Local Copy) or the C:\Program Files\Web Scraper Plus+\Download folder. Then copy the address or drag the file into the datapage editor. Now you should see the same problem that you do with the package and be able to fix it.
A good way to avoid this and just an all around good practice is to create a package that navigates once to every level of a site (i.e. Listings, Next Pages, Details).
Then just use the downloaded pages to build your datapages and you'll never have this problem again.
Hint: Double click or right-click -> View Local Copy on the URL in the Package execution summary to open the downloaded file. Then copy the URL into your datapage.