Sharing an experience solving the remote connection issue with Codex:

My phone's ChatGPT wanted to remotely control Codex on my Mac, but it kept showing "Waiting for Desktop," and scanning the QR code had no response.
Initially, I thought it was a problem with the VPN, nodes, or subscription configuration, so I tested back and forth between Korea/Japan/Netherlands, but nothing worked.
After spending a lot of time retrying, I finally checked the local Codex logs and discovered that the Mac remote enrollment was blocked by the server with a 403:
Multi-factor authentication required
In other words, you might think the pairing between your phone and computer failed, but in reality, the desktop account hadn't completed the necessary MFA level.
I enabled Google two-factor authentication, re-logged into Codex, and after the verification level increased, it finally worked.
Problems like this are especially common when switching between multiple accounts on: phone, Mac, ChatGPT Web, and Codex, or right after changing subscriptions, logging in, or device trust status.
Personal maintenance during the Agent era will increasingly resemble this: on the surface, it looks like a network issue, but at the core, it could be account, permissions, device trust, OAuth, MFA, or remote host status tangled together. Without logs and agent assistance, relying solely on the UI to guess makes it nearly impossible to troubleshoot.