I'm at the step of "Review your order" of Finish & File section. After I click "start" button, the system keeps showing there is a system error. What should I do?

The topic of the error is "Hmm, looks like we hit a slight snag in this section" with message "Let's get you back to your taxes. Make sure your Internet is connected, and then select Try again, refresh your browser, or check back in a few minutes."