Fix Gemini Canvas App Issue

I need help with a very simple app created on Gemini Canvas. It was working fine but now has completely stopped working. I'm sure an expert in Gemini can quickly identify and resolve the issue. The app is small and straightforward, so I'm looking for someone who can troubleshoot efficiently and get it running again. It just a local app, nothing complicated. Also, I know longer have the preview window while using Gemini Canvas. It would be great if someone knew how to get that back. I've tried every suggestion I can find online.