@duramax, that was an excellent summing up of DOA-101 couse and remedy. I might add one more, though I am NOT familiar with the build (design) of this light.
Maybe the body/tube is a fraction too short.
In general the head end of the body/tube is not anodised from the threads up to the very end. Therefore the front end almost every time makes good contact, no matter how far it is screwed in.
The tail end of the body is often all anodised except for the very last end. By unscrewing a litte bit the tail-cap is can be used as a physical lockout. But in rare occasion this end of the body/tube is not long enough for touching the switch board or retaining ring, thus causing a permanent lockout. Have you tried to reverse the body/tube? The wire to bridge can help you find the cause. It is also a help to detect if the retaining ring of the switch board is not tightened enough.
BTW have you checked the retaining ring of the driver? Is it firmly screwed in?