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At the price point for these lights, it wouldn't really make sense to ship the unit back to China and ship a replacement out, so Orca generally just ships a new unit out when needed.
I would look at the switch first. Inexpensive magnetic switches fail sometimes. I think you could check this be removing the tail cap and using a wire to short the flashlight body to the negative battery terminal. If the D550 is like the non-diving lights I'm used to, the tailcap switch is a momentary-off design, so just holding a wire across the gap and intermittently lifting then reconnecting it will cycle through the different modes.
OrcaTorch is in China.
-Z