Ive tried selecting any character for the new one , and all my choices error to invalid character

Sorry for my asking but where do u get that coupon?

Okay so, it has to be an older released character you choose. (no hashashin or anything newer) and you have to have an open slot with a non made alt yet, and used on an account that is 50+currently. Its touchy and almost useless for most of us but its pretty much a "free old alt to 50+ if you still have the slot ticket".