This advice is brought to you by Marcus Porcaro.
When creating a table in Canvas, the border lines appear invisible initially. It’s perfectly fine to leave it this way, however if you would like to add a border line you can.
To do so, edit the page in the Rich Content Editor.
Click inside the table to bring up the table options.
Click the far left option titled Table Properties.
When you’re satisfied, click Ok and then Save.