Well, you got me there. I never heard of a 209 adaptor for a sidelock Hawken.
Where did you get that? I would be interested in one for the TC.
I will bet you could use a trick that I use sometimes when loading a hunting load.
I would pull the nipple, and put a few grains of powder right there in the drum. I don't mean 2 measured grains, I mean 2, 3, or 4 individual little grains of black powder.
Never had a misfire when doing that. I bet if you tried that with the Blackhorn it would light up.