MGS9029: review host failed
The server answered 502 bad gateway because the review host did not take a
publish or a reply. Nothing was sent.
[MGS9029] publish: no pull request is open for this branch
see: .../MGS9029.md
Why
Publish and reply put sentences in front of colleagues, so they fail loudly: a reader told a send succeeded when it did not will never find out. The message carries the host's own reason after the op name (no open review, no credential, an HTTP status from the host).
Resolution
Act on the reason it names, then send again. The drafts stay in the session until they are published.