Welcome to the community!
Yes Windows remote control support for Codex rolled out yesterday (May, 29), so it’s hard to tell from the outside whether this is a bug, rollout delay or an app/account state issue.
I’d first check that both the Windows Codex app and the ChatGPT mobile app are fully updated, then sign out/in on both sides and restart the Windows host.
If it still connects but shows a blank mobile Codex view, I’d report it with device OS/version, Codex app version, ChatGPT app version, account plan, region, screenshots and the time it happened. You can do that though Help.