Have you exceeded the limit of most open games you can host at one time?
If you haven’t:
1) Refresh the page
2) If that doesn’t work:
2.1) Restart your router/modem -> refresh page
2.2) Restart your device -> refresh page
2.3) If none of the above work, send a bug report Help->Contact->Report Bug (https://www.warzone.com/ReportBug)