As far back as I can remember people converting to a Clark board for the first time, not placing a jumper on the SW pins has usually been the main reason for the no power issue.
The information actually has been listed under the Assembly Guide area in the online guide and in the PDF TK20 guide file I put together from Clark's info a few years ago, but it's rather, let's say, less emphatically stated as it probably should be . . . though the new text is written in red in the online guide, lol. The text is still the same as the old PDF, but a new image has been added to the online guide which shows the SW pin location with a jumper installed under the suggestion to add the jumper to short the pins when using a power switch on the battery cable path.
Install a switch cable (for example, HL Smoke Unit Switch Cable) to SW connector( Switch Cable Port) as power switch.
Because HL tank already have power switch on battery cable path, so additional switch is not required, just to use a jumper to short pins in SW Cable port or connect a switch cable and keep it switched on.
~ Craig ~