HR tag and tables not appearing on wordpress theme

Not sure why this theme does this, but it sets the border property of the hr elements to 0 so nothing shows. What you need to do is add a CSS rule like this:

.post-content hr {
   border: 1px solid #000;
}

You can change the color to whatever you want, I’ve set it to black (#000), but a gray color like #ccc might be better. You can also adjust the line thickness by changing the first parameter. You can see other values for styling the border property here.

You can do the same thing with the table cells:

.post-content td {
   border: 1px solid #000;
   padding: 5px;
}

I added a padding property so the text isn’t butt-up against the borders.

So normally I include a warning about not making changes to the theme’s style.css file, because the next time you update the theme, your changes will be lost, but it sounds like maybe there will be no more updates to the theme? At some point, you should think about switching themes, then, because you are going to want to use a theme that stays up to date with the latest security patches and WordPress core updates.