There are two possible reasons why you're seeing an empty paper trading balance:
No paper funds deposited
You'll need to add paper funds before you can start paper trading - just like you'd need real money in a live trading account! For more information on how to deposit the paper money you can check out this article.
You can also deposit paper funds straight from the Bot Doctor: click the orange "Issues" button in the bottom-right corner of your Paper Trading bot's dashboard and deposit the quote currency with one click.
You have reset your paper balance
If you've reset your paper trading balance, it will return to zero. Want to learn more about resets and what to consider? Check out this article.