The page loaded, but the application did not. That almost always means the built files are not the ones being served.
npm run build and the
build output directory to dist, then deploy again.
npm install and then npm run dev, and open the address it
prints.
/assets/ points at a missing or misconfigured deploy.
Nothing has been lost. Letters are stored in this browser and are not affected by a failed page load. Full instructions are in the project README.