The Vercel Analytics page will initialize after a single data point is collected in the time range you're looking at, and at most after 30 minutes has elapsed. For more information on when data points are collected, please check out our Analytics Documentation.
For a page or URL to appear on the Vercel Analytics page, a minimum of 10 data points is required in the time range you're looking at. It is important to note that only fresh page loads report Web Vitals. Client-side page transitions will not.