Does anyone have any (current) contact info? neal@bangg… and his assistant’s email (heyanqing1@bangg…) both bounce. I found those on this site last night, but they were posted here about two years ago.
Many thanks for your help!
Two remarks.
1st/ you have a deal with a seller. You give Banggood $$, Banggood gives you a working item.
If the item does not do what it is supposed to do, contact the seller: Banggood.
The manufacturer has a deal with Banggood, that deal is completed. You’re no part of it.
2nd/ you have tried to reach very old contacts. Neal quit his job at Banggood ages ago.
You can find Banggood in this forum in the menu under commercial sellers: send them a PM.
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Though the A6 seems to be everybody’s favorite: not for me. People like to mod it.
My motto is: if it works, don’t fix it, don’t even take it apart. Because bad tolerances of the body.
To fix them is quite easy, only after you have discovered what parts don’t (properly) connect.
Unlike you might think, the switch can be the issue. A clicking sound itself proves nothing.
Have you tried to fasten all retaining rings?
Put the light on its head. Remove the tailcap piece. Connect battery and rear end of the body with a piece of copper wire. What does it do?
If you have more recent contact information than that posted in this forum- would you kindly provide it? In order to PM, I have to have the recipient’s name. I don’t have that information.
I am an EE, embedded systems designer. I have troubleshot this, yes including using a jumper cable to make the connection at the tailpiece. I didn’t say, and do not think it is the switch. I understand how product transactions are supposed to take place. That, of course, explains why I want to contact the mfg. I will search for that information with the clues your provided.
The seller you need to PM is: Banggood . AFAIK the manufacturer isn’t a member here.
Sorry can’t help you any further. As an EE you know that you never must postpone untill tomorrow what others can do for you today. Matthew 7:7: Ask and it will be given to you; seek and you will find; knock and the door will be opened to you.
Good advice Henk4U2. 
Thanks very much for the contact info. For some reason I thought BLF was in the name of the MFG. I can go on… 
BLF just means the light was designed by BudgetLightForum members. I believe these may have been made by Manker at some point and sold under different house brand names.
We have members that designed the driver and the manufacturer worked with us to put the light together in a way we here directed, with emitter choices guided by us as well. Hence the tribute to BLF on the flashlight. There have now been quite a few of these collaborations with good success.