Thank you for the post, the other issue is a separate one that's fortunately long since resolved.
I can't make any promises as I don't have tools to add characters, but I'd like to gather info.
When was Caustic unlocked for you, and did you use coins or tokens?
I can see a Crypto unlock recently, I take it that this worked without issue?
Can you provide an image of his Banners > Trackers page, that should show enough gameplay stats to prove previous ownership/playtime.