I figured out how to get lines - but it's pretty clunky.  You need to add the following to each <td> element.  As in, you need to go into the html and find each <td> and add this to the very end

style="border:1px solid black;"

example:
<td style="border:1px solid black;">

It would be lovely if there was an easier way.   I also need to have some tables entirely white (rather than striped).  The code isn't working for that.  Any ideas?

I need it for table 2 on this page: https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/08%3A_Inheritance/8.5%3A_Complex_Inheritance

The band in the middle makes the pictures look weird.  White would look better.  Not a bit deal if it's not possible.