It depends what kind of Token you purchased, Valorei.
If it was from the Auction House… as the others indicated, you cannot sell the Token back to the Auction House. Once purchased it can only be used for Game Time or Battle.net Balance. As Inna mentioned though, if your Alt WoW license is on the same Battle.net Account, you should be able to use the token from the character selection screen.
If you purchased it from the Shop, then it can only be placed on the Auction House to sell for gold.
As of right now, for buying/selling WoW Tokens on the Auction House, it does appear to be disabled. It may be associated with the extended maintenance that the shop went under earlier today. It is being looked into.