MAV_RESULT 3 (3) — UNSUPPORTED — command not supported

The autopilot does not implement this command at all. Distinct from DENIED, where it is implemented but refused.

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Diagnosis

When you hit this

Sending a command from a newer MAVLink dialect to older firmware.
A command supported by one autopilot family but not another.
A vehicle-type-specific command sent to the wrong vehicle type.

Resolution

How to fix it

Check the firmware's supported command set
Autopilot documentation lists supported MAV_CMD values per version.
Fall back to an older equivalent
Many newer commands have a deprecated predecessor that older firmware accepts.

Normalization

What Forge does about it

This is a configuration or addressing mistake on the wire, upstream of anything Forge sees. Where Forge helps is the step after you fix it: once the point returns data, its vendor tag name maps to a canonical field automatically, so you do not also have to hand-maintain a name table for every point you just re-addressed.