Due to a server crash for Nintendo’s eShop, their Pokémon Bank service (which released on December 25th) was subsequently taken down from the 3DS eShop.
So far, no word yet on when the service will be restored but once it returns, the 30 free-trial period will be reset. North America and Europe was slated to receive the service on December 27th but currently the release date on the app in the eShop states “TBD” (To Be Decided). The Western release date seems to have been pushed back.
Pokémon Bank was the main cause of the massive server crash, thanks to a huge traffic spike once the Bank was available for download. The crash affects both Wii U and 3DS servers thanks to the recent linking of online services, courtesy of the new update.