ZoomMtg.join() silently fails after Marketplace review session – WebSocket connects but participant never joins

Meeting SDK Type and Version: Web Meeting SDK 4.0.7 (General App / User Managed)

Description:
Our app was working correctly until March 23, 2026, when a Zoom Marketplace reviewer accessed our app for functional review. Since then, ZoomMtg.join() is called with valid credentials but no success or error callback is ever triggered — the participant never appears in the meeting.

What we have verified:

  • SDK Key, ZAK token (fresh from /v2/users/me/zak via OAuth), and JWT signature are all present and valid
  • ZoomMtg.init() completes successfully
  • ZoomMtg.join() is called with correct parameters
  • The WebSocket connection is established (HTTP 101 Switching Protocols)
  • Binary messages are exchanged (handshake + heartbeats of 16B)
  • The second WebSocket closes with a 21B message (clean close)
  • No error callbacks are fired, no error messages in console
  • Reproduced in Chrome, Edge, incognito mode
  • Reproduced with multiple meeting IDs including our own Personal Meeting Room
  • Reproduced with fresh OAuth tokens after full logout/re-authorization
  • This occurs even when joining meetings hosted by our own developer account

Console log (always ends here, no further output):
externalController sdk init
success load webim
success load tp
success load jsmedia
pre load wasm success
langDir …
you can remove sdkKey from join params since v4.0.0.
[silence — no success, no error]

Browser: Chrome 144, Edge 144, Windows 10

Question: Could the Marketplace review session have changed the state of our app or account on Zoom’s servers in a way that is silently blocking joins? We have been unable to resolve this from our side despite extensive debugging. Any guidance would be appreciated.

Update: I found this related thread: Join failing when using new App Client ID/Secret instead of legacy SDK keys. In that case, Zoom confirmed and fixed a bug on March 19 where new Client ID/Secret credentials failed for external meetings. My app uses Client ID/Secret as SDK Key/Secret (General App, no legacy SDK keys), and the issue started on March 23 after a Marketplace reviewer accessed the app. Could this be related to an incomplete fix rollout, or a similar server-side issue affecting my specific app/account?