Client sees no update

Check	Meaning
Version status	Must be published with a ready line (packs_ready_at stamped)
os/arch	Matching version line required
Incomplete gray	Non-allowlisted (including anonymous) keep the old version
Method	POST check only; GET is 404
Channel token	Wrong token is not 403; that hidden channel is skipped
MIN_OS_NOT_MET	OS/API below the line floor
NO_SAFE_TARGET / VERSION_REVOKED	No safe target after revoke/yank

204 means up to date, not failure. 304 is ETag.