1. General Troubleshooting Principles (Do these three steps first)

1. Confirm Subscription: Is AppSubscription created? (No subscription = Definitely no data)
2. Confirm Connection: Is App connection status Connected/Failed? (Fix connection first if Failed)
3. Confirm Topic & Payload: Is topic rendered correctly? Does payload meet consumption side expectation?

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2. Common Symptoms → Quick Positioning

2.1 App shows Connected, but no data on platform side

• Is corresponding uplink mapping enabled (e.g., telemetry.enabled)?
• Is topic rendered as empty (Template variable missing)?
• Is platform side consuming on the correct topic?
• Does QueuePolicy.dropPolicy=Discard cause massive drops (Under high load)?

2.2 App shows Failed (Auth/Network/TLS)

• Kafka: bootstrap servers, SASL/TLS config, ACL
• Pulsar: service_url, token, tenant/namespace permission
• ThingsBoard: token/username/password, certificate path, Provision key/secret
• OPC UA Server: Port conflict, Certificate/PKI, client trust

2.3 Queue Full (QueueFull / outbound queue rejected)

• Main queue capacity too small
• Platform side consumption slow (lag/backlog)
• Topic too fine-grained causing partition hotspot
• Mixed high-frequency telemetry and critical control

2.4 Downlink message sent but gateway did not execute

• downlink topic must be exact match (No template)
• Does AckPolicy/FailurePolicy cause message to be drop/ignore?
• When using MappedJson, does filter match?
• Is payload shape correct (event.kind and data fields)?