I don't actually know why it's not working for you, hmm. I know some layouts remove borders on tables but looking at your journal, the Janelle Monae table from here is fine and they're the exact same code...

Okay, so, I switched to the same layout as you and tried posting the table and it works for me: https://fsf-mod.dreamwidth.org/7835.html

Have you tried copy/pasting the code again and reposting the entry? I know that's not a super-helpful suggestion but if it's happening multiple times then I'm a bit stumped as to what's going on, but I will keep looking at it, sorry! :(