How do I get my avatoars on this website for battletech?

[Havamal]

So I entered the code on my backer page and it says that the code was already used and is no longer valid. Any ideas?

This kind of error message happens in a lot of online instances, often its a false error message.
I would;

1. double check that you entered the correct code
2. sync steam account (if you use such)
3. log out and log in again.
4. go to 'owned items' and click sync.
5. wait for a day or two, it has been a delayed process for many .
6. Finally, if none of that worked. Only then would I contact HBS