I bought Marine Right Leg Motion Trail from the market. Yes, I activated it in my inventory. But it doesn't show up, why is that?

Also, it says that I have 0 ingame earnings for DarkJustice1... I have a different username ingame that on the forum, so how do I make that work?

The second one, Is probably Just a bug
As for the First Problem some times it takes a few for the to show up ingame, How long did you wait

I figured it was simultaneous , so I didn't really wait..

Does it work Now?

try these commands if you are in a hurry...
/dl darkjustice1
wait for response that you have been downloaded
/lp 1 darkjustice1
this will show your new textures and items on tori.
edit: of course you will have to be moving to see your new trail.

First how long did you wait?
Second are you using a different computer?

I've waited this long (since I've posted this originally). It still doesn't work. I'll try those commands, I suppose.

EDIT: The commands don't seem to work... Well, unless, does it matter if it's freeplay or not?

commands will work in freeplay fine, I can see you have the item in your activated (check good)
I checked I can see your trail on in freeplay.
My bad above I should have said /lp 0 darkjustice1
/lp 1 darkjustice1 this places the items on uke
If you do both you will see yourself fighting yourself.

It works now. Thank you.

But it still won't transfer the TC from ingame to on the forum..

I think tc from in game to forum and vice versa is essentially instant. However, there is a bit of lag to see forum/game tc changes. For example you sell an item in market gain tc, you won't see it instantly in game, however you can still bet it. If it updated all the time perhaps this would use too much of our communities resources or crash the servers with too much info. For the same reason various services like search are limited. This is somewhat conjectural, but fits my understanding.
Reread your initial question...

Forum name is the same as your in game name, so you have 2 accounts. Items and tc won't transfer between those separate accounts without using the send tools in the shop section.