Zoom SDK – Consistent “Signature Invalid” and “Failed to Join Meeting” Errors (Web and Windows SDK)

We’ve been attempting to build an automated interviewer bot using the Zoom Meeting SDK and have run into consistent issues with JWT authentication and joining meetings across both the Windows SDK (v6.4.10.64484) and the Web SDK.

:locked_with_key: App & Credentials

  • Meeting SDK App Type
    Created in Zoom App Marketplace
  • Client ID (appKey): KRuSXYtVQIO1YqsMuNTdw
  • Client Secret: Zs6uLtTXjpDQ3N8XZsDqzVeJB6WEO3dQ

:test_tube: Testing Environment

Windows SDK:

  • Version: 6.4.10.64484
  • Language: C++
  • Auth: JWT
  • Platform: Local build using Visual Studio

Web SDK:

  • Auth: Signature generated via JWT using the same app credentials

:red_exclamation_mark:Observed Issues

On Windows SDK:

  • Successfully calls SDKAuth(authContext) with generated JWT
  • Returns AUTHRET_SUCCESS
  • Fails at Join() with error SDKERR_UNAUTHENTICATION (8)
  • Same behavior observed even after deferring Join() to onAuthenticationReturn() callback

On Web SDK:

  • Signature is generated as per docs using appKey, appSecret, iat, exp, etc.

  • Results in:

{type: ‘INVALID_SIGNATURE’, reason: ‘Signature is invalid.’}

What We’ve Verified
• JWT structure is valid (tested on jwtio and Zoom JWT Test link of Zoom itself)
• Token is not expired and includes appKey, iat, exp, tokenExp
• JWT token works until authentication step, but meeting join fails
• The meeting ID being used is 9753616449
(Hosted under our own Zoom account — also verified)
• Same behavior when creating fresh meetings from the same Zoom account
• The same issue reproduces on both Windows SDK and Web SDK, indicating either:
• SDK is rejecting valid tokens
• Or something is wrong with how the SDK ties token to host account or meeting

:puzzle_piece: Request
• Can Zoom please confirm whether this is a known issue with the Windows/Web Meeting SDK in v6.4.10?
• Is there any way to validate whether a Meeting ID is resolvable by an SDK-authenticated bot?
• Is there a way to debug “Failed to join meeting” (SDKERR_UNAUTHENTICATION) more precisely?

We’ve exhausted all documentation and forum advice — any support would be greatly appreciated.