| 400 | Missing token parameter, Malformed token | The URL was altered |
| 400 | Token purpose must be 'connect' for /start, Token purpose must be 'manage' for this endpoint | A manage link opened on /start or the reverse |
| 401 | Invalid token: … | Bad signature, wrong app secret, or expired link |
| 403 | This link has already been used | Connect link started twice, or manage link used for a second deletion |
| 409 | This ChatGPT account is already connected to another user of this app… | The account belongs to another user of your app; the link is spent |
| 404 | App not found, User not found | Unknown appId, or a manage link for a user who never connected |