I've uploaded the error log to pastebin with id Qe0e1Uw2

Since I can neither post the error log here nor the link to it I don't see any other way than this. Hope you can find it if you need it.

  @Vincent-TP I've received the mail and sent you the log and also the link to the github issue where some people already tried to find out what the source of the issue might be. Hope this helps in quickly finding and hopefully fixing the problem. Thanks.

  @Vincent-TP What is the corresponding Open API? Can you please link me documentation for the API that is appropriate for my controller version?
 

Controller version: 6.2.0.17 (local, self-hosted)

We tested the Open API /clients endpoint using OAuth2 client credentials authentication. Token acquisition works, and other
endpoints work fine — but /clients returns "General error" in every variation.

What works:

 - POST /openapi/authorize/token?grant_type=client_credentials → errorCode: 0, valid access token returned
 - GET /openapi/v1/{omadacId}/sites?page=1&pageSize=10 → errorCode: 0, returns site data
 - GET /openapi/v1/{omadacId}/sites/{siteId}/devices?page=1&pageSize=5 → errorCode: 0, returns all 11 devices with full details

What fails: All of these return {"errorCode": -1, "msg": "General error."} with HTTP 200:

 - GET /openapi/v1/{omadacId}/sites/{siteId}/clients?page=1&pageSize=5
 - GET /openapi/v1/{omadacId}/sites/{siteId}/clients?page=1&pageSize=5&filters.active=true
 - GET /openapi/v1/{omadacId}/sites/{siteId}/clients?pageSize=5&page=1

Both Authorization: AccessToken=<token> and Authorization: Bearer <token> header formats were tried. The AccessToken= format reaches
the endpoint (returns the errorCode -1 JSON). The Bearer format returns a different error about token expiry, suggesting it's a
valid auth path but may handle token format differently.

Conclusion: The /clients "General error" bug affects both the Web API (/api/v2/sites/{siteId}/clients) and the Open API (
/openapi/v1/{omadacId}/sites/{siteId}/clients) on Controller 6.2.0.17. The TP-Link recommendation to "use the Open API" does not
resolve the issue on this version.