One of the most frustrating issues with WordPress are blank page errors ("WSOD"). How to troubleshoot something when there is no information?
WooCart has error handling and shows you an ID for every error. You can then use this ID to find the root cause in Error Logs.
Copy the error ID you've been shown and go to Error Logs. Enter the ID, and it shows you exactly what happened.
Even if you're not a developer, you can find the culprit (usually a plugin), which you can then disable and bring your store back online in just a few seconds.