This likely means that your theme is removing the borders with its CSS code. Can you please send me a link to the page with the table where this problem happens, so that I can take a direct look? Thanks!
Thanks for the information about the padding. Yes, I will adjust the code.
Regarding the borders, here is how it looks like in the backend:
As you can see, there are vertical borders in that table. On the frontend, the vertical borders are not showing (please check the first screenshot in the thread).
note that the layout/styling of the “Edit” screen is not a visual representation of how the table will look like on the frontend! To get an initial idea of the styling, you can use the “Preview” button on the “Edit” screen. (But that’s also not always accurate, as the theme usually applies styling to tables as well.)
Also note that vertical borders in tables are considered detrimental for legibility, which is why the default styling doesn’t set them. You can however achieve that, e.g. by adding this to the “Custom CSS” text area on the “Plugin Options” screen of TablePress: