First, the two-minute checks: try the site from your phone's cellular data (rules out your Wi-Fi), and if you recently pointed your own domain at us, DNS changes can take a little while to reach everyone.
Our own monitoring checks every customer surface around the clock and pages us when anything is wrong — most incidents are being worked before anyone writes in. If your site is unreachable and the checks above don't explain it, email hello@onesmallprompt.com with your address and "DOWN" in the subject; those get read first.