docs: add troubleshooting guide for missing Actuators tab

docs/en/qgc-user-guide/setup_view/px4/actuators.md

@@ -26,3 +26,50 @@ With the safety switch toggled, individual actuator sliders appear for testing e
 ## Actuator Actions
 
 Dynamic action buttons (e.g., beep, identify, 3D mode) are shown based on the vehicle's actuator configuration. The **motor identification** feature spins motors one at a time to verify correct wiring and rotation direction.
+
+## Troubleshooting a Missing Actuators Page
+
+The Actuators page is shown when QGroundControl receives and initializes the
+vehicle's `COMP_METADATA_TYPE_ACTUATORS` component metadata. The firmware
+version alone does not determine whether the page is available. If the
+metadata is unavailable, cannot be initialized, or its top-level `show-ui-if`
+condition evaluates to false, QGroundControl uses the legacy Motors page
+instead.
+
+### Capture Diagnostic Logs
+
+1. Open **Application Settings > App Log Viewer**.
+2. Click **Categories** and enable these categories:
+   - `Vehicle.Actuators.PX4AutoPilotPlugin`
+   - `ComponentInformation.RequestMetaDataTypeStateMachine`
+   - `Vehicle.FTPManager`
+3. Connect the vehicle. If it is already connected, disconnect and reconnect
+   it so that QGroundControl requests the component metadata again.
+4. Open **Vehicle Setup** and check whether **Actuators** or **Motors** is
+   available.
+5. Return to **App Log Viewer** and click **Save**. Keep the saved app log
+   unchanged when attaching it to a support request.
+
+The metadata URI can use MAVLink FTP (`mavlinkftp://`) or HTTP. QGroundControl
+tries the primary URI first and then the fallback URI advertised by the
+vehicle.
+
+### Read the Diagnostic Messages
+
+| Log category | Message or pattern | Meaning |
+| --- | --- | --- |
+| `Vehicle.Actuators.PX4AutoPilotPlugin` | `Vehicle did not provide actuators metadata via component information` | No actuator metadata was received from the vehicle. |
+| `Vehicle.Actuators.PX4AutoPilotPlugin` | `Actuators initialization failed` | Metadata was received but could not be parsed or initialized. |
+| `Vehicle.Actuators.PX4AutoPilotPlugin` | `Condition 'show-ui-if' evaluated to false` | The metadata deliberately hides the page for the current vehicle configuration. |
+| `ComponentInformation.RequestMetaDataTypeStateMachine` | `primary failed, requesting metadata (fallback) from ...` | The primary metadata URI failed and QGroundControl is trying the fallback URI. |
+| `ComponentInformation.RequestMetaDataTypeStateMachine` | `FTP download failed` or `HTTP download failed` | The selected transport could not download the metadata. An HTTP status such as `404` identifies a missing or incorrect URL. |
+| `ComponentInformation.RequestMetaDataTypeStateMachine` | `failed to load metadata (primary and fallback)` | Both metadata URIs failed, so the Actuators page cannot be initialized. |
+| `Vehicle.FTPManager` | `Download fromCompId`, `Nak - ...`, or timeout messages | Details of the MAVLink FTP request and any vehicle-side error. |
+
+### Include This Information in a Support Request
+
+Include the QGroundControl version and build, PX4 firmware version, vehicle
+type, connection type, whether the legacy Motors page appears, and the saved
+app log. If the log contains a fallback or download error, include the full
+line with the URI and error text. Also mention whether reconnecting the vehicle
+changes the result.